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	$91.85	13.746%	$104.4757	$104.48	$104.50	$104.50
Purchase #2	$117.73	11.408%	$131.1606	$131.16	$131.15	$131.20
Purchase #3	$134.33	11.333%	$149.5536	$149.55	$149.55	$149.60
Purchase #4	$127.43	11.325%	$141.8614	$141.86	$141.85	$141.90
Purchase #5	$191.92	4.461%	$200.4816	$200.48	$200.50	$200.50
Purchase #6	$109.99	6.150%	$116.7544	$116.75	$116.75	$116.80
Purchase #7	$63.77	10.160%	$70.249	$70.25	$70.25	$70.20
7 purchase totals =	$837.02		$914.5363	$914.53	$914.55	$914.70