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	$232.89	13.550%	$264.4466	$264.45	$264.45	$264.40
Purchase #2	$65.97	10.808%	$73.1	$73.10	$73.10	$73.10
Purchase #3	$171.40	11.547%	$191.1916	$191.19	$191.20	$191.20
Purchase #4	$242.87	5.617%	$256.512	$256.51	$256.50	$256.50
Purchase #5	$148.88	10.648%	$164.7327	$164.73	$164.75	$164.70
Purchase #6	$41.31	5.616%	$43.63	$43.63	$43.65	$43.60
Purchase #7	$138.62	8.634%	$150.5885	$150.59	$150.60	$150.60
7 purchase totals =	$1,041.94		$1,144.2014	$1,144.20	$1,144.25	$1,144.10