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	$137.79	7.144%	$147.6337	$147.63	$147.65	$147.60
Purchase #2	$182.25	7.458%	$195.8422	$195.84	$195.85	$195.80
Purchase #3	$63.52	12.221%	$71.2828	$71.28	$71.30	$71.30
Purchase #4	$13.45	3.264%	$13.889	$13.89	$13.90	$13.90
Purchase #5	$105.72	11.144%	$117.5014	$117.50	$117.50	$117.50
Purchase #6	$148.55	3.504%	$153.7552	$153.76	$153.75	$153.80
Purchase #7	$48.42	12.190%	$54.3224	$54.32	$54.30	$54.30
7 purchase totals =	$699.70		$754.2267	$754.22	$754.25	$754.20