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	$151.43	9.695%	$166.1111	$166.11	$166.10	$166.10
Purchase #2	$137.61	9.754%	$151.0325	$151.03	$151.05	$151.00
Purchase #3	$34.61	9.626%	$37.9416	$37.94	$37.95	$37.90
Purchase #4	$229.60	5.510%	$242.251	$242.25	$242.25	$242.30
Purchase #5	$147.94	3.620%	$153.2954	$153.30	$153.30	$153.30
Purchase #6	$110.73	11.437%	$123.3942	$123.39	$123.40	$123.40
Purchase #7	$55.38	5.607%	$58.4852	$58.49	$58.50	$58.50
7 purchase totals =	$867.30		$932.5110	$932.51	$932.55	$932.50