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	$48.43	9.349%	$52.9577	$52.96	$52.95	$53.00
Purchase #2	$39.76	10.379%	$43.8867	$43.89	$43.90	$43.90
Purchase #3	$174.40	11.770%	$194.9269	$194.93	$194.95	$194.90
Purchase #4	$104.64	13.447%	$118.7109	$118.71	$118.70	$118.70
Purchase #5	$173.72	8.573%	$188.613	$188.61	$188.60	$188.60
Purchase #6	$155.80	10.381%	$171.9736	$171.97	$171.95	$172.00
Purchase #7	$237.82	3.251%	$245.5515	$245.55	$245.55	$245.60
7 purchase totals =	$934.57		$1,016.6203	$1,016.62	$1,016.60	$1,016.70