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	$111.88	10.482%	$123.6073	$123.61	$123.60	$123.60
Purchase #2	$141.95	6.489%	$151.1611	$151.16	$151.15	$151.20
Purchase #3	$144.61	5.706%	$152.8614	$152.86	$152.85	$152.90
Purchase #4	$132.97	3.668%	$137.8473	$137.85	$137.85	$137.80
Purchase #5	$118.46	3.650%	$122.7838	$122.78	$122.80	$122.80
Purchase #6	$211.35	5.583%	$223.1497	$223.15	$223.15	$223.10
Purchase #7	$167.96	7.546%	$180.6343	$180.63	$180.65	$180.60
7 purchase totals =	$1,029.18		$1,092.0449	$1,092.04	$1,092.05	$1,092.00