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	$167.55	11.316%	$186.51	$186.51	$186.50	$186.50
Purchase #2	$152.44	7.626%	$164.0651	$164.07	$164.05	$164.10
Purchase #3	$180.63	3.764%	$187.4289	$187.43	$187.45	$187.40
Purchase #4	$65.28	7.396%	$70.1081	$70.11	$70.10	$70.10
Purchase #5	$88.37	7.499%	$94.9969	$95.00	$95.00	$95.00
Purchase #6	$128.48	12.799%	$144.9242	$144.92	$144.90	$144.90
Purchase #7	$64.70	12.167%	$72.572	$72.57	$72.55	$72.60
7 purchase totals =	$847.45		$920.6052	$920.61	$920.55	$920.60