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	$41.46	7.835%	$44.7084	$44.71	$44.70	$44.70
Purchase #2	$173.40	9.151%	$189.2678	$189.27	$189.25	$189.30
Purchase #3	$5.33	10.212%	$5.8743	$5.87	$5.85	$5.90
Purchase #4	$168.46	8.516%	$182.8061	$182.81	$182.80	$182.80
Purchase #5	$83.48	7.158%	$89.4555	$89.46	$89.45	$89.50
Purchase #6	$224.72	7.146%	$240.7785	$240.78	$240.80	$240.80
Purchase #7	$214.98	3.834%	$223.2223	$223.22	$223.20	$223.20
7 purchase totals =	$911.83		$976.1129	$976.12	$976.05	$976.20