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	$143.86	7.787%	$155.0624	$155.06	$155.05	$155.10
Purchase #2	$6.73	10.398%	$7.4298	$7.43	$7.45	$7.40
Purchase #3	$60.35	11.234%	$67.1297	$67.13	$67.15	$67.10
Purchase #4	$85.60	11.564%	$95.4988	$95.50	$95.50	$95.50
Purchase #5	$147.28	4.168%	$153.4186	$153.42	$153.40	$153.40
Purchase #6	$227.69	12.772%	$256.7706	$256.77	$256.75	$256.80
Purchase #7	$135.62	8.798%	$147.5518	$147.55	$147.55	$147.60
7 purchase totals =	$807.13		$882.8617	$882.86	$882.85	$882.90