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	$177.33	7.873%	$191.2912	$191.29	$191.30	$191.30
Purchase #2	$175.30	8.457%	$190.1251	$190.13	$190.15	$190.10
Purchase #3	$79.68	12.353%	$89.5229	$89.52	$89.50	$89.50
Purchase #4	$64.50	11.718%	$72.0581	$72.06	$72.05	$72.10
Purchase #5	$128.33	11.456%	$143.0315	$143.03	$143.05	$143.00
Purchase #6	$189.70	6.748%	$202.501	$202.50	$202.50	$202.50
Purchase #7	$127.83	9.707%	$140.2385	$140.24	$140.25	$140.20
7 purchase totals =	$942.67		$1,028.7683	$1,028.77	$1,028.80	$1,028.70