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	$177.69	9.619%	$194.782	$194.78	$194.80	$194.80
Purchase #2	$146.49	12.683%	$165.0693	$165.07	$165.05	$165.10
Purchase #3	$212.48	5.344%	$223.8349	$223.83	$223.85	$223.80
Purchase #4	$109.32	7.309%	$117.3102	$117.31	$117.30	$117.30
Purchase #5	$170.50	11.425%	$189.9796	$189.98	$190.00	$190.00
Purchase #6	$116.27	6.124%	$123.3904	$123.39	$123.40	$123.40
Purchase #7	$21.52	12.362%	$24.1803	$24.18	$24.20	$24.20
7 purchase totals =	$954.27		$1,038.5467	$1,038.54	$1,038.60	$1,038.60