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	$198.62	4.125%	$206.8131	$206.81	$206.80	$206.80
Purchase #2	$199.37	12.813%	$224.9153	$224.92	$224.90	$224.90
Purchase #3	$131.39	6.449%	$139.8633	$139.86	$139.85	$139.90
Purchase #4	$79.92	13.142%	$90.4231	$90.42	$90.40	$90.40
Purchase #5	$89.83	9.616%	$98.4681	$98.47	$98.45	$98.50
Purchase #6	$225.95	8.560%	$245.2913	$245.29	$245.30	$245.30
Purchase #7	$229.67	11.232%	$255.4665	$255.47	$255.45	$255.50
7 purchase totals =	$1,154.75		$1,261.2407	$1,261.24	$1,261.15	$1,261.30