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	$95.79	3.481%	$99.1244	$99.12	$99.10	$99.10
Purchase #2	$111.66	7.847%	$120.422	$120.42	$120.40	$120.40
Purchase #3	$35.48	4.153%	$36.9535	$36.95	$36.95	$37.00
Purchase #4	$106.27	5.248%	$111.847	$111.85	$111.85	$111.80
Purchase #5	$150.25	3.387%	$155.339	$155.34	$155.35	$155.30
Purchase #6	$148.42	8.813%	$161.5003	$161.50	$161.50	$161.50
Purchase #7	$99.55	4.272%	$103.8028	$103.80	$103.80	$103.80
7 purchase totals =	$747.42		$788.9890	$788.98	$788.95	$788.90