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	$234.35	9.614%	$256.8804	$256.88	$256.90	$256.90
Purchase #2	$106.39	5.793%	$112.5532	$112.55	$112.55	$112.60
Purchase #3	$219.33	8.570%	$238.1266	$238.13	$238.15	$238.10
Purchase #4	$81.98	4.504%	$85.6724	$85.67	$85.65	$85.70
Purchase #5	$184.71	5.305%	$194.5089	$194.51	$194.50	$194.50
Purchase #6	$115.77	12.554%	$130.3038	$130.30	$130.30	$130.30
Purchase #7	$43.67	3.130%	$45.0369	$45.04	$45.05	$45.00
7 purchase totals =	$986.20		$1,063.0822	$1,063.08	$1,063.10	$1,063.10