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	$49.69	6.532%	$52.9358	$52.94	$52.95	$52.90
Purchase #2	$41.97	8.469%	$45.5244	$45.52	$45.50	$45.50
Purchase #3	$131.81	3.517%	$136.4458	$136.45	$136.45	$136.40
Purchase #4	$170.79	8.147%	$184.7043	$184.70	$184.70	$184.70
Purchase #5	$196.27	6.282%	$208.5997	$208.60	$208.60	$208.60
Purchase #6	$200.44	5.802%	$212.0695	$212.07	$212.05	$212.10
Purchase #7	$201.53	3.860%	$209.3091	$209.31	$209.30	$209.30
7 purchase totals =	$992.50		$1,049.5886	$1,049.59	$1,049.55	$1,049.50