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	$177.65	10.791%	$196.8202	$196.82	$196.80	$196.80
Purchase #2	$36.73	13.619%	$41.7323	$41.73	$41.75	$41.70
Purchase #3	$56.61	12.364%	$63.6093	$63.61	$63.60	$63.60
Purchase #4	$228.61	9.350%	$249.985	$249.99	$250.00	$250.00
Purchase #5	$116.77	6.601%	$124.478	$124.48	$124.50	$124.50
Purchase #6	$229.70	6.612%	$244.8878	$244.89	$244.90	$244.90
Purchase #7	$67.39	8.108%	$72.854	$72.85	$72.85	$72.90
7 purchase totals =	$913.46		$994.3666	$994.37	$994.40	$994.40