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	$140.73	7.352%	$151.0765	$151.08	$151.10	$151.10
Purchase #2	$200.45	11.487%	$223.4757	$223.48	$223.50	$223.50
Purchase #3	$207.52	7.588%	$223.2666	$223.27	$223.25	$223.30
Purchase #4	$239.50	6.641%	$255.4052	$255.41	$255.40	$255.40
Purchase #5	$192.51	11.323%	$214.3079	$214.31	$214.30	$214.30
Purchase #6	$61.92	10.258%	$68.2718	$68.27	$68.25	$68.30
Purchase #7	$221.89	7.209%	$237.8861	$237.89	$237.90	$237.90
7 purchase totals =	$1,264.52		$1,373.6898	$1,373.71	$1,373.70	$1,373.80