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	$14.84	6.580%	$15.8165	$15.82	$15.80	$15.80
Purchase #2	$40.91	6.413%	$43.5336	$43.53	$43.55	$43.50
Purchase #3	$50.97	11.203%	$56.6802	$56.68	$56.70	$56.70
Purchase #4	$42.52	10.293%	$46.8966	$46.90	$46.90	$46.90
Purchase #5	$111.82	11.503%	$124.6827	$124.68	$124.70	$124.70
Purchase #6	$67.70	6.645%	$72.1987	$72.20	$72.20	$72.20
Purchase #7	$36.38	3.327%	$37.5904	$37.59	$37.60	$37.60
7 purchase totals =	$365.14		$397.3987	$397.40	$397.45	$397.40