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	$48.45	11.792%	$54.1632	$54.16	$54.15	$54.20
Purchase #2	$172.55	9.277%	$188.5575	$188.56	$188.55	$188.60
Purchase #3	$64.35	10.568%	$71.1505	$71.15	$71.15	$71.20
Purchase #4	$89.78	7.492%	$96.5063	$96.51	$96.50	$96.50
Purchase #5	$175.67	10.620%	$194.3262	$194.33	$194.35	$194.30
Purchase #6	$206.71	8.503%	$224.2866	$224.29	$224.30	$224.30
Purchase #7	$164.94	8.248%	$178.5443	$178.54	$178.55	$178.50
7 purchase totals =	$922.45		$1,007.5346	$1,007.54	$1,007.55	$1,007.60