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	$207.71	7.745%	$223.7971	$223.80	$223.80	$223.80
Purchase #2	$83.79	7.450%	$90.0324	$90.03	$90.05	$90.00
Purchase #3	$65.31	10.455%	$72.1382	$72.14	$72.15	$72.10
Purchase #4	$228.34	7.685%	$245.8879	$245.89	$245.90	$245.90
Purchase #5	$165.66	8.795%	$180.2298	$180.23	$180.25	$180.20
Purchase #6	$188.52	13.865%	$214.6583	$214.66	$214.65	$214.70
Purchase #7	$115.46	3.187%	$119.1397	$119.14	$119.15	$119.10
7 purchase totals =	$1,054.79		$1,145.8834	$1,145.89	$1,145.95	$1,145.80