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	$99.51	11.648%	$111.1009	$111.10	$111.10	$111.10
Purchase #2	$56.42	9.745%	$61.9181	$61.92	$61.90	$61.90
Purchase #3	$97.37	11.363%	$108.4342	$108.43	$108.45	$108.40
Purchase #4	$30.70	3.457%	$31.7613	$31.76	$31.75	$31.80
Purchase #5	$136.43	11.629%	$152.2954	$152.30	$152.30	$152.30
Purchase #6	$186.70	12.217%	$209.5091	$209.51	$209.50	$209.50
Purchase #7	$198.81	12.173%	$223.0111	$223.01	$223.00	$223.00
7 purchase totals =	$805.94		$898.0301	$898.03	$898.00	$898.00