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	$114.28	6.243%	$121.4145	$121.41	$121.40	$121.40
Purchase #2	$87.56	3.385%	$90.5239	$90.52	$90.50	$90.50
Purchase #3	$63.29	3.314%	$65.3874	$65.39	$65.40	$65.40
Purchase #4	$184.30	6.122%	$195.5828	$195.58	$195.60	$195.60
Purchase #5	$152.89	3.452%	$158.1678	$158.17	$158.15	$158.20
Purchase #6	$125.60	5.226%	$132.1639	$132.16	$132.15	$132.20
Purchase #7	$216.82	5.793%	$229.3804	$229.38	$229.40	$229.40
7 purchase totals =	$944.74		$992.6207	$992.61	$992.60	$992.70