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	$163.46	4.292%	$170.4757	$170.48	$170.50	$170.50
Purchase #2	$68.37	5.120%	$71.8705	$71.87	$71.85	$71.90
Purchase #3	$248.85	10.627%	$275.2953	$275.30	$275.30	$275.30
Purchase #4	$182.51	4.841%	$191.3453	$191.35	$191.35	$191.30
Purchase #5	$11.47	12.285%	$12.8791	$12.88	$12.90	$12.90
Purchase #6	$249.68	10.440%	$275.7466	$275.75	$275.75	$275.70
Purchase #7	$191.95	3.827%	$199.2959	$199.30	$199.30	$199.30
7 purchase totals =	$1,116.29		$1,196.9084	$1,196.93	$1,196.95	$1,196.90