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	$202.50	3.464%	$209.5146	$209.51	$209.50	$209.50
Purchase #2	$54.54	7.166%	$58.4483	$58.45	$58.45	$58.40
Purchase #3	$142.54	5.690%	$150.6505	$150.65	$150.65	$150.70
Purchase #4	$25.45	10.479%	$28.1169	$28.12	$28.10	$28.10
Purchase #5	$57.82	6.185%	$61.3962	$61.40	$61.40	$61.40
Purchase #6	$165.65	10.673%	$183.3298	$183.33	$183.35	$183.30
Purchase #7	$27.35	13.595%	$31.0682	$31.07	$31.05	$31.10
7 purchase totals =	$675.85		$722.5245	$722.53	$722.50	$722.50