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	$137.65	3.352%	$142.264	$142.26	$142.25	$142.30
Purchase #2	$227.80	5.567%	$240.4816	$240.48	$240.50	$240.50
Purchase #3	$172.68	10.221%	$190.3296	$190.33	$190.35	$190.30
Purchase #4	$192.57	10.169%	$212.1524	$212.15	$212.15	$212.20
Purchase #5	$229.31	6.233%	$243.6029	$243.60	$243.60	$243.60
Purchase #6	$100.35	3.188%	$103.5492	$103.55	$103.55	$103.50
Purchase #7	$125.95	3.679%	$130.5837	$130.58	$130.60	$130.60
7 purchase totals =	$1,186.31		$1,262.9634	$1,262.95	$1,263.00	$1,263.00