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	$88.26	4.596%	$92.3164	$92.32	$92.30	$92.30
Purchase #2	$58.90	10.809%	$65.2665	$65.27	$65.25	$65.30
Purchase #3	$174.70	12.694%	$196.8764	$196.88	$196.90	$196.90
Purchase #4	$144.27	6.361%	$153.447	$153.45	$153.45	$153.40
Purchase #5	$213.64	12.551%	$240.454	$240.45	$240.45	$240.50
Purchase #6	$242.35	13.325%	$274.6431	$274.64	$274.65	$274.60
Purchase #7	$112.59	10.279%	$124.1631	$124.16	$124.15	$124.20
7 purchase totals =	$1,034.71		$1,147.1665	$1,147.17	$1,147.15	$1,147.20