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	$105.45	9.263%	$115.2178	$115.22	$115.20	$115.20
Purchase #2	$108.54	13.741%	$123.4545	$123.45	$123.45	$123.50
Purchase #3	$131.70	4.221%	$137.2591	$137.26	$137.25	$137.30
Purchase #4	$76.39	12.677%	$86.074	$86.07	$86.05	$86.10
Purchase #5	$244.80	7.644%	$263.5125	$263.51	$263.50	$263.50
Purchase #6	$183.50	7.110%	$196.5469	$196.55	$196.55	$196.50
Purchase #7	$89.61	10.106%	$98.666	$98.67	$98.65	$98.70
7 purchase totals =	$939.99		$1,020.7308	$1,020.73	$1,020.65	$1,020.80