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	$124.92	3.803%	$129.6707	$129.67	$129.65	$129.70
Purchase #2	$92.53	11.490%	$103.1617	$103.16	$103.15	$103.20
Purchase #3	$243.77	5.114%	$256.2364	$256.24	$256.25	$256.20
Purchase #4	$159.67	8.273%	$172.8795	$172.88	$172.90	$172.90
Purchase #5	$58.32	12.150%	$65.4059	$65.41	$65.40	$65.40
Purchase #6	$170.39	12.521%	$191.7245	$191.72	$191.70	$191.70
Purchase #7	$29.71	5.550%	$31.3589	$31.36	$31.35	$31.40
7 purchase totals =	$879.31		$950.4376	$950.44	$950.40	$950.50