Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$203.39	5.588%	$214.7554	$214.76	$214.75	$214.80
Purchase #2	$103.72	11.712%	$115.8677	$115.87	$115.85	$115.90
Purchase #3	$203.47	9.517%	$222.8342	$222.83	$222.85	$222.80
Purchase #4	$201.88	10.710%	$223.5013	$223.50	$223.50	$223.50
Purchase #5	$155.29	6.174%	$164.8776	$164.88	$164.90	$164.90
Purchase #6	$144.31	13.730%	$164.1238	$164.12	$164.10	$164.10
Purchase #7	$109.28	3.736%	$113.3627	$113.36	$113.35	$113.40
7 purchase totals =	$1,121.34		$1,219.3227	$1,219.32	$1,219.30	$1,219.40