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	$214.40	3.182%	$221.2222	$221.22	$221.20	$221.20
Purchase #2	$177.55	7.789%	$191.3794	$191.38	$191.40	$191.40
Purchase #3	$13.35	3.689%	$13.8425	$13.84	$13.85	$13.80
Purchase #4	$121.72	5.429%	$128.3282	$128.33	$128.35	$128.30
Purchase #5	$53.49	10.871%	$59.3049	$59.30	$59.30	$59.30
Purchase #6	$32.65	9.862%	$35.8699	$35.87	$35.85	$35.90
Purchase #7	$90.52	3.153%	$93.3741	$93.37	$93.35	$93.40
7 purchase totals =	$703.68		$743.3212	$743.31	$743.30	$743.30