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	$181.91	9.368%	$198.9513	$198.95	$198.95	$199.00
Purchase #2	$243.63	5.257%	$256.4376	$256.44	$256.45	$256.40
Purchase #3	$44.53	3.652%	$46.1562	$46.16	$46.15	$46.20
Purchase #4	$138.44	5.788%	$146.4529	$146.45	$146.45	$146.50
Purchase #5	$180.40	8.661%	$196.0244	$196.02	$196.00	$196.00
Purchase #6	$45.95	10.772%	$50.8997	$50.90	$50.90	$50.90
Purchase #7	$89.45	13.747%	$101.7467	$101.75	$101.75	$101.70
7 purchase totals =	$924.31		$996.6688	$996.67	$996.65	$996.70