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	$129.28	4.159%	$134.6568	$134.66	$134.65	$134.70
Purchase #2	$145.84	11.690%	$162.8887	$162.89	$162.90	$162.90
Purchase #3	$59.72	3.281%	$61.6794	$61.68	$61.70	$61.70
Purchase #4	$176.34	6.790%	$188.3135	$188.31	$188.30	$188.30
Purchase #5	$200.93	9.599%	$220.2173	$220.22	$220.20	$220.20
Purchase #6	$102.56	8.642%	$111.4232	$111.42	$111.40	$111.40
Purchase #7	$135.38	4.872%	$141.9757	$141.98	$142.00	$142.00
7 purchase totals =	$950.05		$1,021.1546	$1,021.16	$1,021.15	$1,021.20