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	$206.43	4.764%	$216.2643	$216.26	$216.25	$216.30
Purchase #2	$229.47	5.465%	$242.0105	$242.01	$242.00	$242.00
Purchase #3	$9.75	12.120%	$10.9317	$10.93	$10.95	$10.90
Purchase #4	$212.62	9.825%	$233.5099	$233.51	$233.50	$233.50
Purchase #5	$54.55	8.181%	$59.0127	$59.01	$59.00	$59.00
Purchase #6	$209.89	11.487%	$234.0001	$234.00	$234.00	$234.00
Purchase #7	$19.53	10.240%	$21.5299	$21.53	$21.55	$21.50
7 purchase totals =	$942.24		$1,017.2591	$1,017.25	$1,017.25	$1,017.20