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	$144.82	3.291%	$149.586	$149.59	$149.60	$149.60
Purchase #2	$68.82	13.419%	$78.055	$78.06	$78.05	$78.10
Purchase #3	$33.44	13.369%	$37.9106	$37.91	$37.90	$37.90
Purchase #4	$75.79	10.464%	$83.7207	$83.72	$83.70	$83.70
Purchase #5	$162.65	5.330%	$171.3192	$171.32	$171.30	$171.30
Purchase #6	$29.98	5.365%	$31.5884	$31.59	$31.60	$31.60
Purchase #7	$26.25	7.828%	$28.3049	$28.30	$28.30	$28.30
7 purchase totals =	$541.75		$580.4848	$580.49	$580.45	$580.50