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	$180.85	13.621%	$205.4836	$205.48	$205.50	$205.50
Purchase #2	$115.71	10.410%	$127.7554	$127.76	$127.75	$127.80
Purchase #3	$192.31	10.537%	$212.5737	$212.57	$212.55	$212.60
Purchase #4	$44.34	10.389%	$48.9465	$48.95	$48.95	$48.90
Purchase #5	$169.82	10.317%	$187.3403	$187.34	$187.35	$187.30
Purchase #6	$203.54	3.340%	$210.3382	$210.34	$210.35	$210.30
Purchase #7	$178.77	5.757%	$189.0618	$189.06	$189.05	$189.10
7 purchase totals =	$1,085.34		$1,181.4995	$1,181.50	$1,181.50	$1,181.50