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	$49.46	9.304%	$54.0618	$54.06	$54.05	$54.10
Purchase #2	$88.77	5.578%	$93.7216	$93.72	$93.70	$93.70
Purchase #3	$176.69	9.165%	$192.8836	$192.88	$192.90	$192.90
Purchase #4	$236.41	9.515%	$258.9044	$258.90	$258.90	$258.90
Purchase #5	$20.29	10.663%	$22.4535	$22.45	$22.45	$22.50
Purchase #6	$249.73	10.308%	$275.4722	$275.47	$275.45	$275.50
Purchase #7	$181.76	8.340%	$196.9188	$196.92	$196.90	$196.90
7 purchase totals =	$1,003.11		$1,094.4159	$1,094.40	$1,094.35	$1,094.50