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	$67.29	6.297%	$71.5273	$71.53	$71.55	$71.50
Purchase #2	$59.64	3.729%	$61.864	$61.86	$61.85	$61.90
Purchase #3	$248.47	12.416%	$279.32	$279.32	$279.30	$279.30
Purchase #4	$93.90	7.732%	$101.1603	$101.16	$101.15	$101.20
Purchase #5	$240.99	9.832%	$264.6841	$264.68	$264.70	$264.70
Purchase #6	$83.92	12.868%	$94.7188	$94.72	$94.70	$94.70
Purchase #7	$219.97	10.734%	$243.5816	$243.58	$243.60	$243.60
7 purchase totals =	$1,014.18		$1,116.8561	$1,116.85	$1,116.85	$1,116.90