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	$135.54	10.675%	$150.0089	$150.01	$150.00	$150.00
Purchase #2	$33.85	3.173%	$34.9241	$34.92	$34.90	$34.90
Purchase #3	$56.53	4.666%	$59.1677	$59.17	$59.15	$59.20
Purchase #4	$210.33	11.788%	$235.1237	$235.12	$235.10	$235.10
Purchase #5	$216.26	12.702%	$243.7293	$243.73	$243.75	$243.70
Purchase #6	$190.88	13.754%	$217.1336	$217.13	$217.15	$217.10
Purchase #7	$143.55	11.679%	$160.3152	$160.32	$160.30	$160.30
7 purchase totals =	$986.94		$1,100.4025	$1,100.40	$1,100.35	$1,100.30