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	$207.84	12.114%	$233.0177	$233.02	$233.00	$233.00
Purchase #2	$84.61	8.462%	$91.7697	$91.77	$91.75	$91.80
Purchase #3	$185.70	12.496%	$208.9051	$208.91	$208.90	$208.90
Purchase #4	$165.82	10.656%	$183.4898	$183.49	$183.50	$183.50
Purchase #5	$136.88	5.479%	$144.3797	$144.38	$144.40	$144.40
Purchase #6	$191.79	13.335%	$217.3652	$217.37	$217.35	$217.40
Purchase #7	$77.28	7.800%	$83.3078	$83.31	$83.30	$83.30
7 purchase totals =	$1,049.92		$1,162.2350	$1,162.25	$1,162.20	$1,162.30