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	$248.58	13.567%	$282.3048	$282.30	$282.30	$282.30
Purchase #2	$123.77	6.216%	$131.4635	$131.46	$131.45	$131.50
Purchase #3	$147.28	3.451%	$152.3626	$152.36	$152.35	$152.40
Purchase #4	$83.36	7.210%	$89.3703	$89.37	$89.35	$89.40
Purchase #5	$36.56	11.130%	$40.6291	$40.63	$40.65	$40.60
Purchase #6	$58.55	6.575%	$62.3997	$62.40	$62.40	$62.40
Purchase #7	$227.88	8.846%	$248.0383	$248.04	$248.05	$248.00
7 purchase totals =	$925.98		$1,006.5683	$1,006.56	$1,006.55	$1,006.60