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	$248.77	8.175%	$269.1069	$269.11	$269.10	$269.10
Purchase #2	$231.52	4.313%	$241.5055	$241.51	$241.50	$241.50
Purchase #3	$86.79	5.513%	$91.5747	$91.57	$91.55	$91.60
Purchase #4	$181.83	12.651%	$204.8333	$204.83	$204.85	$204.80
Purchase #5	$109.81	6.837%	$117.3177	$117.32	$117.30	$117.30
Purchase #6	$17.28	8.538%	$18.7554	$18.76	$18.75	$18.80
Purchase #7	$55.64	11.208%	$61.8761	$61.88	$61.90	$61.90
7 purchase totals =	$931.64		$1,004.9696	$1,004.98	$1,004.95	$1,005.00