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	$220.25	11.195%	$244.907	$244.91	$244.90	$244.90
Purchase #2	$153.32	6.216%	$162.8504	$162.85	$162.85	$162.90
Purchase #3	$55.68	7.309%	$59.7497	$59.75	$59.75	$59.70
Purchase #4	$29.70	12.218%	$33.3287	$33.33	$33.35	$33.30
Purchase #5	$124.77	3.285%	$128.8687	$128.87	$128.85	$128.90
Purchase #6	$80.81	13.351%	$91.5989	$91.60	$91.60	$91.60
Purchase #7	$210.76	8.408%	$228.4807	$228.48	$228.50	$228.50
7 purchase totals =	$875.29		$949.7841	$949.79	$949.80	$949.80