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	$147.94	3.557%	$153.2022	$153.20	$153.20	$153.20
Purchase #2	$107.76	4.729%	$112.856	$112.86	$112.85	$112.90
Purchase #3	$24.38	12.829%	$27.5077	$27.51	$27.50	$27.50
Purchase #4	$169.54	3.409%	$175.3196	$175.32	$175.30	$175.30
Purchase #5	$147.46	8.315%	$159.7213	$159.72	$159.70	$159.70
Purchase #6	$88.57	13.778%	$100.7732	$100.77	$100.75	$100.80
Purchase #7	$53.27	6.123%	$56.5317	$56.53	$56.55	$56.50
7 purchase totals =	$738.92		$785.9117	$785.91	$785.85	$785.90