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	$47.88	11.129%	$53.2086	$53.21	$53.20	$53.20
Purchase #2	$154.48	5.337%	$162.7246	$162.72	$162.70	$162.70
Purchase #3	$40.58	3.797%	$42.1208	$42.12	$42.10	$42.10
Purchase #4	$137.60	5.233%	$144.8006	$144.80	$144.80	$144.80
Purchase #5	$21.33	6.512%	$22.719	$22.72	$22.70	$22.70
Purchase #6	$211.29	6.378%	$224.7661	$224.77	$224.75	$224.80
Purchase #7	$54.33	10.360%	$59.9586	$59.96	$59.95	$60.00
7 purchase totals =	$667.49		$710.2983	$710.30	$710.20	$710.30