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	$91.26	3.586%	$94.5326	$94.53	$94.55	$94.50
Purchase #2	$238.58	8.844%	$259.68	$259.68	$259.70	$259.70
Purchase #3	$60.32	8.619%	$65.519	$65.52	$65.50	$65.50
Purchase #4	$75.99	3.745%	$78.8358	$78.84	$78.85	$78.80
Purchase #5	$102.95	6.755%	$109.9043	$109.90	$109.90	$109.90
Purchase #6	$14.32	6.696%	$15.2789	$15.28	$15.30	$15.30
Purchase #7	$82.50	8.657%	$89.642	$89.64	$89.65	$89.60
7 purchase totals =	$665.92		$713.3926	$713.39	$713.45	$713.30