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	$132.75	8.832%	$144.4745	$144.47	$144.45	$144.50
Purchase #2	$169.65	13.326%	$192.2576	$192.26	$192.25	$192.30
Purchase #3	$79.93	12.455%	$89.8853	$89.89	$89.90	$89.90
Purchase #4	$215.59	12.349%	$242.2132	$242.21	$242.20	$242.20
Purchase #5	$95.40	11.283%	$106.164	$106.16	$106.15	$106.20
Purchase #6	$142.86	12.647%	$160.9275	$160.93	$160.95	$160.90
Purchase #7	$8.33	6.417%	$8.8645	$8.86	$8.85	$8.90
7 purchase totals =	$844.51		$944.7866	$944.78	$944.75	$944.90