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	$13.62	7.213%	$14.6024	$14.60	$14.60	$14.60
Purchase #2	$46.86	9.178%	$51.1608	$51.16	$51.15	$51.20
Purchase #3	$62.27	5.690%	$65.8132	$65.81	$65.80	$65.80
Purchase #4	$28.90	12.599%	$32.5411	$32.54	$32.55	$32.50
Purchase #5	$58.51	4.535%	$61.1634	$61.16	$61.15	$61.20
Purchase #6	$46.40	9.623%	$50.8651	$50.87	$50.85	$50.90
Purchase #7	$202.35	12.538%	$227.7206	$227.72	$227.70	$227.70
7 purchase totals =	$458.91		$503.8666	$503.86	$503.80	$503.90