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	$112.53	3.572%	$116.5496	$116.55	$116.55	$116.50
Purchase #2	$77.34	13.564%	$87.8304	$87.83	$87.85	$87.80
Purchase #3	$83.52	8.773%	$90.8472	$90.85	$90.85	$90.80
Purchase #4	$99.74	4.536%	$104.2642	$104.26	$104.25	$104.30
Purchase #5	$111.73	6.287%	$118.7545	$118.75	$118.75	$118.80
Purchase #6	$98.89	12.162%	$110.917	$110.92	$110.90	$110.90
Purchase #7	$165.69	5.644%	$175.0415	$175.04	$175.05	$175.00
7 purchase totals =	$749.44		$804.2044	$804.20	$804.20	$804.10