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	$144.80	7.702%	$155.9525	$155.95	$155.95	$156.00
Purchase #2	$57.31	7.854%	$61.8111	$61.81	$61.80	$61.80
Purchase #3	$129.80	8.766%	$141.1783	$141.18	$141.20	$141.20
Purchase #4	$162.92	7.349%	$174.893	$174.89	$174.90	$174.90
Purchase #5	$95.32	5.657%	$100.7123	$100.71	$100.70	$100.70
Purchase #6	$167.81	11.644%	$187.3498	$187.35	$187.35	$187.30
Purchase #7	$32.31	12.300%	$36.2841	$36.28	$36.30	$36.30
7 purchase totals =	$790.27		$858.1811	$858.17	$858.20	$858.20