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	$155.95	8.825%	$169.7126	$169.71	$169.70	$169.70
Purchase #2	$205.29	13.242%	$232.4745	$232.47	$232.45	$232.50
Purchase #3	$191.64	6.745%	$204.5661	$204.57	$204.55	$204.60
Purchase #4	$174.58	6.518%	$185.9591	$185.96	$185.95	$186.00
Purchase #5	$100.75	10.803%	$111.634	$111.63	$111.65	$111.60
Purchase #6	$65.26	11.309%	$72.6403	$72.64	$72.65	$72.60
Purchase #7	$50.92	5.122%	$53.5281	$53.53	$53.55	$53.50
7 purchase totals =	$944.39		$1,030.5147	$1,030.51	$1,030.50	$1,030.50