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	$204.52	5.641%	$216.057	$216.06	$216.05	$216.10
Purchase #2	$212.40	11.284%	$236.3672	$236.37	$236.35	$236.40
Purchase #3	$128.52	11.126%	$142.8191	$142.82	$142.80	$142.80
Purchase #4	$72.25	6.545%	$76.9788	$76.98	$77.00	$77.00
Purchase #5	$69.72	12.129%	$78.1763	$78.18	$78.20	$78.20
Purchase #6	$244.29	10.266%	$269.3688	$269.37	$269.35	$269.40
Purchase #7	$124.76	11.535%	$139.1511	$139.15	$139.15	$139.20
7 purchase totals =	$1,056.46		$1,158.9183	$1,158.93	$1,158.90	$1,159.10