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	$132.57	9.137%	$144.6829	$144.68	$144.70	$144.70
Purchase #2	$104.95	4.742%	$109.9267	$109.93	$109.95	$109.90
Purchase #3	$125.82	8.207%	$136.146	$136.15	$136.15	$136.10
Purchase #4	$66.84	8.477%	$72.506	$72.51	$72.50	$72.50
Purchase #5	$99.76	4.610%	$104.3589	$104.36	$104.35	$104.40
Purchase #6	$105.45	4.477%	$110.171	$110.17	$110.15	$110.20
Purchase #7	$164.28	3.571%	$170.1464	$170.15	$170.15	$170.10
7 purchase totals =	$799.67		$847.9379	$847.95	$847.95	$847.90