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	$113.75	3.236%	$117.431	$117.43	$117.45	$117.40
Purchase #2	$233.70	10.520%	$258.2852	$258.29	$258.30	$258.30
Purchase #3	$55.69	8.831%	$60.608	$60.61	$60.60	$60.60
Purchase #4	$224.47	11.363%	$249.9765	$249.98	$250.00	$250.00
Purchase #5	$114.94	3.345%	$118.7847	$118.78	$118.80	$118.80
Purchase #6	$195.59	11.754%	$218.5796	$218.58	$218.60	$218.60
Purchase #7	$80.39	11.570%	$89.6911	$89.69	$89.70	$89.70
7 purchase totals =	$1,018.53		$1,113.3561	$1,113.36	$1,113.45	$1,113.40