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	$132.29	13.152%	$149.6888	$149.69	$149.70	$149.70
Purchase #2	$5.74	11.676%	$6.4102	$6.41	$6.40	$6.40
Purchase #3	$28.32	9.387%	$30.9784	$30.98	$31.00	$31.00
Purchase #4	$152.47	11.401%	$169.8531	$169.85	$169.85	$169.90
Purchase #5	$72.33	9.112%	$78.9207	$78.92	$78.90	$78.90
Purchase #6	$63.77	11.794%	$71.291	$71.29	$71.30	$71.30
Purchase #7	$238.53	8.300%	$258.328	$258.33	$258.35	$258.30
7 purchase totals =	$693.45		$765.4702	$765.47	$765.50	$765.50