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	$131.57	12.784%	$148.3899	$148.39	$148.40	$148.40
Purchase #2	$85.90	4.639%	$89.8849	$89.88	$89.90	$89.90
Purchase #3	$50.94	9.284%	$55.6693	$55.67	$55.65	$55.70
Purchase #4	$213.28	3.784%	$221.3505	$221.35	$221.35	$221.40
Purchase #5	$211.30	6.571%	$225.1845	$225.18	$225.20	$225.20
Purchase #6	$195.99	7.216%	$210.1326	$210.13	$210.15	$210.10
Purchase #7	$146.34	10.505%	$161.713	$161.71	$161.70	$161.70
7 purchase totals =	$1,035.32		$1,112.3247	$1,112.31	$1,112.35	$1,112.40