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	$98.72	13.319%	$111.8685	$111.87	$111.85	$111.90
Purchase #2	$37.31	4.199%	$38.8766	$38.88	$38.90	$38.90
Purchase #3	$16.74	9.858%	$18.3902	$18.39	$18.40	$18.40
Purchase #4	$223.45	6.590%	$238.1754	$238.18	$238.20	$238.20
Purchase #5	$19.43	10.117%	$21.3957	$21.40	$21.40	$21.40
Purchase #6	$8.43	12.427%	$9.4776	$9.48	$9.50	$9.50
Purchase #7	$21.43	10.118%	$23.5983	$23.60	$23.60	$23.60
7 purchase totals =	$425.51		$461.7823	$461.80	$461.85	$461.90