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	$104.78	5.521%	$110.5649	$110.56	$110.55	$110.60
Purchase #2	$82.61	6.680%	$88.1283	$88.13	$88.15	$88.10
Purchase #3	$132.60	8.678%	$144.107	$144.11	$144.10	$144.10
Purchase #4	$68.81	11.713%	$76.8697	$76.87	$76.85	$76.90
Purchase #5	$98.26	13.591%	$111.6145	$111.61	$111.60	$111.60
Purchase #6	$131.85	12.245%	$147.995	$148.00	$148.00	$148.00
Purchase #7	$102.81	6.505%	$109.4978	$109.50	$109.50	$109.50
7 purchase totals =	$721.72		$788.7772	$788.78	$788.75	$788.80