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	$63.47	6.642%	$67.6857	$67.69	$67.70	$67.70
Purchase #2	$61.28	6.323%	$65.1547	$65.15	$65.15	$65.20
Purchase #3	$159.72	7.503%	$171.7038	$171.70	$171.70	$171.70
Purchase #4	$60.94	4.858%	$63.9005	$63.90	$63.90	$63.90
Purchase #5	$62.41	12.694%	$70.3323	$70.33	$70.35	$70.30
Purchase #6	$196.37	11.822%	$219.5849	$219.58	$219.60	$219.60
Purchase #7	$175.85	6.485%	$187.2539	$187.25	$187.25	$187.30
7 purchase totals =	$780.04		$845.6158	$845.60	$845.65	$845.70