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	$219.34	11.501%	$244.5663	$244.57	$244.55	$244.60
Purchase #2	$71.63	6.286%	$76.1327	$76.13	$76.15	$76.10
Purchase #3	$45.49	4.492%	$47.5334	$47.53	$47.55	$47.50
Purchase #4	$95.87	9.335%	$104.8195	$104.82	$104.80	$104.80
Purchase #5	$224.41	5.507%	$236.7683	$236.77	$236.75	$236.80
Purchase #6	$48.83	7.148%	$52.3204	$52.32	$52.30	$52.30
Purchase #7	$85.29	5.358%	$89.8598	$89.86	$89.85	$89.90
7 purchase totals =	$790.86		$852.0004	$852.00	$851.95	$852.00