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	$109.25	11.648%	$121.9754	$121.98	$122.00	$122.00
Purchase #2	$160.76	13.147%	$181.8951	$181.90	$181.90	$181.90
Purchase #3	$135.80	10.333%	$149.8322	$149.83	$149.85	$149.80
Purchase #4	$143.89	5.640%	$152.0054	$152.01	$152.00	$152.00
Purchase #5	$173.33	4.720%	$181.5112	$181.51	$181.50	$181.50
Purchase #6	$146.37	12.342%	$164.435	$164.44	$164.45	$164.40
Purchase #7	$92.83	11.645%	$103.6401	$103.64	$103.65	$103.60
7 purchase totals =	$962.23		$1,055.2944	$1,055.31	$1,055.35	$1,055.20