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	$45.98	13.584%	$52.2259	$52.23	$52.25	$52.20
Purchase #2	$18.25	5.767%	$19.3025	$19.30	$19.30	$19.30
Purchase #3	$49.86	9.498%	$54.5957	$54.60	$54.60	$54.60
Purchase #4	$124.72	13.351%	$141.3714	$141.37	$141.35	$141.40
Purchase #5	$15.69	13.415%	$17.7948	$17.79	$17.80	$17.80
Purchase #6	$98.71	10.770%	$109.3411	$109.34	$109.35	$109.30
Purchase #7	$30.91	8.355%	$33.4925	$33.49	$33.50	$33.50
7 purchase totals =	$384.12		$428.1239	$428.12	$428.15	$428.10