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	$73.45	3.667%	$76.1434	$76.14	$76.15	$76.10
Purchase #2	$136.45	6.468%	$145.2756	$145.28	$145.30	$145.30
Purchase #3	$152.60	4.460%	$159.406	$159.41	$159.40	$159.40
Purchase #4	$30.78	3.632%	$31.8979	$31.90	$31.90	$31.90
Purchase #5	$149.73	11.563%	$167.0433	$167.04	$167.05	$167.00
Purchase #6	$84.71	8.478%	$91.8917	$91.89	$91.90	$91.90
Purchase #7	$83.70	13.850%	$95.2925	$95.29	$95.30	$95.30
7 purchase totals =	$711.42		$766.9504	$766.95	$767.00	$766.90