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	$100.61	7.678%	$108.3348	$108.33	$108.35	$108.30
Purchase #2	$62.49	7.620%	$67.2517	$67.25	$67.25	$67.30
Purchase #3	$138.77	8.298%	$150.2851	$150.29	$150.30	$150.30
Purchase #4	$232.36	10.597%	$256.9832	$256.98	$257.00	$257.00
Purchase #5	$181.28	5.144%	$190.605	$190.61	$190.60	$190.60
Purchase #6	$83.53	5.700%	$88.2912	$88.29	$88.30	$88.30
Purchase #7	$30.26	6.867%	$32.338	$32.34	$32.35	$32.30
7 purchase totals =	$829.30		$894.0890	$894.09	$894.15	$894.10