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	$184.71	13.703%	$210.0208	$210.02	$210.00	$210.00
Purchase #2	$64.85	11.158%	$72.086	$72.09	$72.10	$72.10
Purchase #3	$111.53	6.615%	$118.9077	$118.91	$118.90	$118.90
Purchase #4	$127.70	6.192%	$135.6072	$135.61	$135.60	$135.60
Purchase #5	$17.31	7.125%	$18.5433	$18.54	$18.55	$18.50
Purchase #6	$91.56	12.151%	$102.6855	$102.69	$102.70	$102.70
Purchase #7	$125.86	4.210%	$131.1587	$131.16	$131.15	$131.20
7 purchase totals =	$723.52		$789.0092	$789.02	$789.00	$789.00