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	$70.79	9.282%	$77.3607	$77.36	$77.35	$77.40
Purchase #2	$89.71	10.333%	$98.9797	$98.98	$99.00	$99.00
Purchase #3	$11.73	10.363%	$12.9456	$12.95	$12.95	$12.90
Purchase #4	$76.95	4.800%	$80.6436	$80.64	$80.65	$80.60
Purchase #5	$113.31	12.358%	$127.3128	$127.31	$127.30	$127.30
Purchase #6	$234.43	11.540%	$261.4832	$261.48	$261.50	$261.50
Purchase #7	$24.68	4.259%	$25.7311	$25.73	$25.75	$25.70
7 purchase totals =	$621.60		$684.4567	$684.45	$684.50	$684.40