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	$226.68	7.401%	$243.4566	$243.46	$243.45	$243.50
Purchase #2	$24.71	12.636%	$27.8324	$27.83	$27.85	$27.80
Purchase #3	$89.99	11.399%	$100.248	$100.25	$100.25	$100.20
Purchase #4	$59.32	8.528%	$64.3788	$64.38	$64.40	$64.40
Purchase #5	$62.42	10.547%	$69.0034	$69.00	$69.00	$69.00
Purchase #6	$13.46	10.139%	$14.8247	$14.82	$14.80	$14.80
Purchase #7	$169.86	10.331%	$187.4082	$187.41	$187.40	$187.40
7 purchase totals =	$646.44		$707.1521	$707.15	$707.15	$707.10