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	$156.70	11.133%	$174.1454	$174.15	$174.15	$174.10
Purchase #2	$17.99	8.507%	$19.5204	$19.52	$19.50	$19.50
Purchase #3	$149.91	8.787%	$163.0826	$163.08	$163.10	$163.10
Purchase #4	$80.52	11.278%	$89.601	$89.60	$89.60	$89.60
Purchase #5	$79.72	13.634%	$90.589	$90.59	$90.60	$90.60
Purchase #6	$168.69	13.663%	$191.7381	$191.74	$191.75	$191.70
Purchase #7	$99.87	6.388%	$106.2497	$106.25	$106.25	$106.20
7 purchase totals =	$753.40		$834.9262	$834.93	$834.95	$834.80