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	$182.59	13.833%	$207.8477	$207.85	$207.85	$207.80
Purchase #2	$105.47	5.371%	$111.1348	$111.13	$111.15	$111.10
Purchase #3	$139.84	12.104%	$156.7662	$156.77	$156.75	$156.80
Purchase #4	$196.88	9.284%	$215.1583	$215.16	$215.15	$215.20
Purchase #5	$75.71	6.341%	$80.5108	$80.51	$80.50	$80.50
Purchase #6	$87.35	4.596%	$91.3646	$91.36	$91.35	$91.40
Purchase #7	$247.45	4.421%	$258.3898	$258.39	$258.40	$258.40
7 purchase totals =	$1,035.29		$1,121.1722	$1,121.17	$1,121.15	$1,121.20