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	$74.86	13.645%	$85.0746	$85.07	$85.05	$85.10
Purchase #2	$179.58	11.706%	$200.6016	$200.60	$200.60	$200.60
Purchase #3	$55.79	6.137%	$59.2138	$59.21	$59.20	$59.20
Purchase #4	$195.53	6.220%	$207.692	$207.69	$207.70	$207.70
Purchase #5	$156.86	9.401%	$171.6064	$171.61	$171.60	$171.60
Purchase #6	$35.35	7.204%	$37.8966	$37.90	$37.90	$37.90
Purchase #7	$176.40	13.212%	$199.706	$199.71	$199.70	$199.70
7 purchase totals =	$874.37		$961.7910	$961.79	$961.75	$961.80