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	$231.89	10.460%	$256.1457	$256.15	$256.15	$256.10
Purchase #2	$224.88	12.804%	$253.6736	$253.67	$253.65	$253.70
Purchase #3	$158.25	5.811%	$167.4459	$167.45	$167.45	$167.40
Purchase #4	$195.73	10.135%	$215.5672	$215.57	$215.55	$215.60
Purchase #5	$190.48	4.431%	$198.9202	$198.92	$198.90	$198.90
Purchase #6	$56.46	5.414%	$59.5167	$59.52	$59.50	$59.50
Purchase #7	$30.83	13.258%	$34.9174	$34.92	$34.90	$34.90
7 purchase totals =	$1,088.52		$1,186.1867	$1,186.20	$1,186.10	$1,186.10