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	$194.67	13.554%	$221.0556	$221.06	$221.05	$221.10
Purchase #2	$246.80	11.180%	$274.3922	$274.39	$274.40	$274.40
Purchase #3	$144.44	8.490%	$156.703	$156.70	$156.70	$156.70
Purchase #4	$103.83	7.821%	$111.9505	$111.95	$111.95	$112.00
Purchase #5	$178.48	3.741%	$185.1569	$185.16	$185.15	$185.20
Purchase #6	$55.63	6.609%	$59.3066	$59.31	$59.30	$59.30
Purchase #7	$226.53	10.445%	$250.1911	$250.19	$250.20	$250.20
7 purchase totals =	$1,150.38		$1,258.7559	$1,258.76	$1,258.75	$1,258.90