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	$38.75	8.680%	$42.1135	$42.11	$42.10	$42.10
Purchase #2	$126.26	11.786%	$141.141	$141.14	$141.15	$141.10
Purchase #3	$49.82	10.213%	$54.9081	$54.91	$54.90	$54.90
Purchase #4	$197.61	13.561%	$224.4079	$224.41	$224.40	$224.40
Purchase #5	$248.42	10.751%	$275.1276	$275.13	$275.15	$275.10
Purchase #6	$196.29	8.679%	$213.326	$213.33	$213.35	$213.30
Purchase #7	$249.33	3.223%	$257.3659	$257.37	$257.35	$257.40
7 purchase totals =	$1,106.48		$1,208.3900	$1,208.40	$1,208.40	$1,208.30