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	$215.81	10.594%	$238.6729	$238.67	$238.65	$238.70
Purchase #2	$27.59	5.241%	$29.036	$29.04	$29.05	$29.00
Purchase #3	$188.92	11.700%	$211.0236	$211.02	$211.00	$211.00
Purchase #4	$72.62	7.700%	$78.2117	$78.21	$78.20	$78.20
Purchase #5	$205.50	12.856%	$231.9191	$231.92	$231.90	$231.90
Purchase #6	$119.74	11.503%	$133.5137	$133.51	$133.50	$133.50
Purchase #7	$130.34	9.651%	$142.9191	$142.92	$142.90	$142.90
7 purchase totals =	$960.52		$1,065.2961	$1,065.29	$1,065.20	$1,065.20