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	$202.89	10.115%	$223.4123	$223.41	$223.40	$223.40
Purchase #2	$101.96	7.123%	$109.2226	$109.22	$109.20	$109.20
Purchase #3	$243.76	6.102%	$258.6342	$258.63	$258.65	$258.60
Purchase #4	$20.42	6.172%	$21.6803	$21.68	$21.70	$21.70
Purchase #5	$74.92	13.559%	$85.0784	$85.08	$85.10	$85.10
Purchase #6	$172.77	10.818%	$191.4603	$191.46	$191.45	$191.50
Purchase #7	$217.83	6.249%	$231.4422	$231.44	$231.45	$231.40
7 purchase totals =	$1,034.55		$1,120.9303	$1,120.92	$1,120.95	$1,120.90