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	$42.46	6.130%	$45.0628	$45.06	$45.05	$45.10
Purchase #2	$67.90	6.508%	$72.3189	$72.32	$72.30	$72.30
Purchase #3	$243.40	5.662%	$257.1813	$257.18	$257.20	$257.20
Purchase #4	$210.97	5.610%	$222.8054	$222.81	$222.80	$222.80
Purchase #5	$155.60	7.125%	$166.6865	$166.69	$166.70	$166.70
Purchase #6	$204.91	5.187%	$215.5387	$215.54	$215.55	$215.50
Purchase #7	$30.58	6.370%	$32.5279	$32.53	$32.55	$32.50
7 purchase totals =	$955.82		$1,012.1215	$1,012.13	$1,012.15	$1,012.10