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	$175.71	7.224%	$188.4033	$188.40	$188.40	$188.40
Purchase #2	$179.28	6.310%	$190.5926	$190.59	$190.60	$190.60
Purchase #3	$57.49	6.677%	$61.3286	$61.33	$61.35	$61.30
Purchase #4	$61.98	5.507%	$65.3932	$65.39	$65.40	$65.40
Purchase #5	$191.64	7.605%	$206.2142	$206.21	$206.20	$206.20
Purchase #6	$153.89	12.268%	$172.7692	$172.77	$172.75	$172.80
Purchase #7	$67.53	11.840%	$75.5256	$75.53	$75.55	$75.50
7 purchase totals =	$887.52		$960.2267	$960.22	$960.25	$960.20