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	$78.47	8.746%	$85.333	$85.33	$85.35	$85.30
Purchase #2	$77.44	12.395%	$87.0387	$87.04	$87.05	$87.00
Purchase #3	$153.43	10.726%	$169.8869	$169.89	$169.90	$169.90
Purchase #4	$248.67	6.247%	$264.2044	$264.20	$264.20	$264.20
Purchase #5	$58.58	3.380%	$60.56	$60.56	$60.55	$60.60
Purchase #6	$227.46	6.559%	$242.3791	$242.38	$242.40	$242.40
Purchase #7	$243.38	8.250%	$263.4589	$263.46	$263.45	$263.50
7 purchase totals =	$1,087.43		$1,172.8610	$1,172.86	$1,172.90	$1,172.90