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	$9.25	10.597%	$10.2302	$10.23	$10.25	$10.20
Purchase #2	$82.90	7.639%	$89.2327	$89.23	$89.25	$89.20
Purchase #3	$32.60	4.656%	$34.1179	$34.12	$34.10	$34.10
Purchase #4	$225.70	4.450%	$235.7437	$235.74	$235.75	$235.70
Purchase #5	$181.83	8.663%	$197.5819	$197.58	$197.60	$197.60
Purchase #6	$61.28	10.500%	$67.7144	$67.71	$67.70	$67.70
Purchase #7	$67.40	6.758%	$71.9549	$71.95	$71.95	$72.00
7 purchase totals =	$660.96		$706.5757	$706.56	$706.60	$706.50