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	$149.78	8.434%	$162.4124	$162.41	$162.40	$162.40
Purchase #2	$33.36	11.231%	$37.1067	$37.11	$37.10	$37.10
Purchase #3	$45.34	3.460%	$46.9088	$46.91	$46.90	$46.90
Purchase #4	$63.80	12.205%	$71.5868	$71.59	$71.60	$71.60
Purchase #5	$146.60	3.738%	$152.0799	$152.08	$152.10	$152.10
Purchase #6	$188.25	8.569%	$204.3811	$204.38	$204.40	$204.40
Purchase #7	$55.84	9.471%	$61.1286	$61.13	$61.15	$61.10
7 purchase totals =	$682.97		$735.6043	$735.61	$735.65	$735.60