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	$127.59	4.156%	$132.8926	$132.89	$132.90	$132.90
Purchase #2	$7.31	8.864%	$7.958	$7.96	$7.95	$8.00
Purchase #3	$112.47	5.760%	$118.9483	$118.95	$118.95	$118.90
Purchase #4	$23.47	3.212%	$24.2239	$24.22	$24.20	$24.20
Purchase #5	$81.53	9.753%	$89.4816	$89.48	$89.50	$89.50
Purchase #6	$9.81	4.158%	$10.2179	$10.22	$10.20	$10.20
Purchase #7	$83.89	7.415%	$90.1104	$90.11	$90.10	$90.10
7 purchase totals =	$446.07		$473.8327	$473.83	$473.80	$473.80