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	$213.48	12.716%	$240.6261	$240.63	$240.65	$240.60
Purchase #2	$83.56	13.729%	$95.032	$95.03	$95.05	$95.00
Purchase #3	$167.43	4.605%	$175.1402	$175.14	$175.15	$175.10
Purchase #4	$58.69	5.450%	$61.8886	$61.89	$61.90	$61.90
Purchase #5	$51.53	11.806%	$57.6136	$57.61	$57.60	$57.60
Purchase #6	$103.87	9.472%	$113.7086	$113.71	$113.70	$113.70
Purchase #7	$139.77	7.534%	$150.3003	$150.30	$150.30	$150.30
7 purchase totals =	$818.33		$894.3094	$894.31	$894.35	$894.20