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	$115.40	13.760%	$131.279	$131.28	$131.30	$131.30
Purchase #2	$91.39	12.714%	$103.0093	$103.01	$103.00	$103.00
Purchase #3	$99.96	3.816%	$103.7745	$103.77	$103.75	$103.80
Purchase #4	$180.95	5.230%	$190.4137	$190.41	$190.40	$190.40
Purchase #5	$197.62	4.579%	$206.669	$206.67	$206.65	$206.70
Purchase #6	$236.66	3.671%	$245.3478	$245.35	$245.35	$245.30
Purchase #7	$115.72	4.144%	$120.5154	$120.52	$120.50	$120.50
7 purchase totals =	$1,037.70		$1,101.0087	$1,101.01	$1,100.95	$1,101.00