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	$191.67	7.222%	$205.5124	$205.51	$205.50	$205.50
Purchase #2	$175.95	10.648%	$194.6852	$194.69	$194.70	$194.70
Purchase #3	$243.89	5.812%	$258.0649	$258.06	$258.05	$258.10
Purchase #4	$85.69	11.176%	$95.2667	$95.27	$95.25	$95.30
Purchase #5	$249.36	13.340%	$282.6246	$282.62	$282.60	$282.60
Purchase #6	$179.38	11.519%	$200.0428	$200.04	$200.05	$200.00
Purchase #7	$60.38	3.255%	$62.3454	$62.35	$62.35	$62.30
7 purchase totals =	$1,186.32		$1,298.5420	$1,298.54	$1,298.50	$1,298.50