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	$224.68	10.628%	$248.559	$248.56	$248.55	$248.60
Purchase #2	$225.39	3.626%	$233.5626	$233.56	$233.55	$233.60
Purchase #3	$231.69	3.711%	$240.288	$240.29	$240.30	$240.30
Purchase #4	$48.73	12.109%	$54.6307	$54.63	$54.65	$54.60
Purchase #5	$25.52	12.319%	$28.6638	$28.66	$28.65	$28.70
Purchase #6	$232.47	11.644%	$259.5388	$259.54	$259.55	$259.50
Purchase #7	$115.83	6.485%	$123.3416	$123.34	$123.35	$123.30
7 purchase totals =	$1,104.31		$1,188.5845	$1,188.58	$1,188.60	$1,188.60