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	$173.68	9.757%	$190.626	$190.63	$190.65	$190.60
Purchase #2	$135.33	7.267%	$145.1644	$145.16	$145.15	$145.20
Purchase #3	$156.39	11.859%	$174.9363	$174.94	$174.95	$174.90
Purchase #4	$105.66	8.846%	$115.0067	$115.01	$115.00	$115.00
Purchase #5	$98.35	7.570%	$105.7951	$105.80	$105.80	$105.80
Purchase #6	$84.42	7.461%	$90.7186	$90.72	$90.70	$90.70
Purchase #7	$72.95	13.107%	$82.5116	$82.51	$82.50	$82.50
7 purchase totals =	$826.78		$904.7587	$904.77	$904.75	$904.70