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	$133.51	11.321%	$148.6247	$148.62	$148.60	$148.60
Purchase #2	$153.38	9.700%	$168.2579	$168.26	$168.25	$168.30
Purchase #3	$79.46	4.512%	$83.0452	$83.05	$83.05	$83.00
Purchase #4	$28.42	4.165%	$29.6037	$29.60	$29.60	$29.60
Purchase #5	$246.94	12.796%	$278.5384	$278.54	$278.55	$278.50
Purchase #6	$232.63	7.467%	$250.0005	$250.00	$250.00	$250.00
Purchase #7	$70.82	10.170%	$78.0224	$78.02	$78.00	$78.00
7 purchase totals =	$945.16		$1,036.0928	$1,036.09	$1,036.05	$1,036.00