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	$156.55	5.477%	$165.1242	$165.12	$165.10	$165.10
Purchase #2	$37.56	9.295%	$41.0512	$41.05	$41.05	$41.10
Purchase #3	$181.37	4.828%	$190.1265	$190.13	$190.15	$190.10
Purchase #4	$106.94	5.782%	$113.1233	$113.12	$113.10	$113.10
Purchase #5	$167.89	9.416%	$183.6985	$183.70	$183.70	$183.70
Purchase #6	$155.94	11.400%	$173.7172	$173.72	$173.70	$173.70
Purchase #7	$100.46	9.408%	$109.9113	$109.91	$109.90	$109.90
7 purchase totals =	$906.71		$976.7522	$976.75	$976.70	$976.70