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	$93.94	12.489%	$105.6722	$105.67	$105.65	$105.70
Purchase #2	$223.52	11.472%	$249.1622	$249.16	$249.15	$249.20
Purchase #3	$151.48	3.128%	$156.2183	$156.22	$156.20	$156.20
Purchase #4	$132.59	7.468%	$142.4918	$142.49	$142.50	$142.50
Purchase #5	$121.90	5.662%	$128.802	$128.80	$128.80	$128.80
Purchase #6	$102.61	13.150%	$116.1032	$116.10	$116.10	$116.10
Purchase #7	$115.97	8.151%	$125.4227	$125.42	$125.40	$125.40
7 purchase totals =	$942.01		$1,023.8724	$1,023.86	$1,023.80	$1,023.90