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	$117.44	5.716%	$124.1529	$124.15	$124.15	$124.20
Purchase #2	$186.91	6.593%	$199.233	$199.23	$199.25	$199.20
Purchase #3	$173.40	5.153%	$182.3353	$182.34	$182.35	$182.30
Purchase #4	$94.70	6.102%	$100.4786	$100.48	$100.50	$100.50
Purchase #5	$184.49	13.809%	$209.9662	$209.97	$209.95	$210.00
Purchase #6	$24.72	7.268%	$26.5166	$26.52	$26.50	$26.50
Purchase #7	$85.38	4.685%	$89.3801	$89.38	$89.40	$89.40
7 purchase totals =	$867.04		$932.0627	$932.07	$932.10	$932.10