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	$187.98	4.585%	$196.5989	$196.60	$196.60	$196.60
Purchase #2	$13.56	10.281%	$14.9541	$14.95	$14.95	$15.00
Purchase #3	$39.26	4.814%	$41.15	$41.15	$41.15	$41.20
Purchase #4	$15.57	9.722%	$17.0837	$17.08	$17.10	$17.10
Purchase #5	$84.47	7.601%	$90.8906	$90.89	$90.90	$90.90
Purchase #6	$163.29	12.583%	$183.8368	$183.84	$183.85	$183.80
Purchase #7	$30.56	6.860%	$32.6564	$32.66	$32.65	$32.70
7 purchase totals =	$534.69		$577.1705	$577.17	$577.20	$577.30