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	$98.77	5.201%	$103.907	$103.91	$103.90	$103.90
Purchase #2	$48.82	9.735%	$53.5726	$53.57	$53.55	$53.60
Purchase #3	$180.66	6.142%	$191.7561	$191.76	$191.75	$191.80
Purchase #4	$174.43	3.456%	$180.4583	$180.46	$180.45	$180.50
Purchase #5	$180.96	8.693%	$196.6909	$196.69	$196.70	$196.70
Purchase #6	$84.81	8.821%	$92.2911	$92.29	$92.30	$92.30
Purchase #7	$70.91	6.631%	$75.612	$75.61	$75.60	$75.60
7 purchase totals =	$839.36		$894.2880	$894.29	$894.25	$894.40