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	$104.74	6.777%	$111.8382	$111.84	$111.85	$111.80
Purchase #2	$55.74	10.863%	$61.795	$61.80	$61.80	$61.80
Purchase #3	$123.69	7.264%	$132.6748	$132.67	$132.65	$132.70
Purchase #4	$125.72	11.206%	$139.8082	$139.81	$139.80	$139.80
Purchase #5	$55.52	11.779%	$62.0597	$62.06	$62.05	$62.10
Purchase #6	$188.40	10.569%	$208.312	$208.31	$208.30	$208.30
Purchase #7	$207.64	11.656%	$231.8425	$231.84	$231.85	$231.80
7 purchase totals =	$861.45		$948.3304	$948.33	$948.30	$948.30