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	$26.31	13.823%	$29.9468	$29.95	$29.95	$29.90
Purchase #2	$222.35	12.548%	$250.2505	$250.25	$250.25	$250.30
Purchase #3	$224.46	12.725%	$253.0225	$253.02	$253.00	$253.00
Purchase #4	$117.49	4.799%	$123.1283	$123.13	$123.15	$123.10
Purchase #5	$29.48	6.475%	$31.3888	$31.39	$31.40	$31.40
Purchase #6	$161.98	7.596%	$174.284	$174.28	$174.30	$174.30
Purchase #7	$140.47	11.830%	$157.0876	$157.09	$157.10	$157.10
7 purchase totals =	$922.54		$1,019.1085	$1,019.11	$1,019.15	$1,019.10