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	$117.49	12.315%	$131.9589	$131.96	$131.95	$132.00
Purchase #2	$233.49	13.452%	$264.8991	$264.90	$264.90	$264.90
Purchase #3	$170.76	7.233%	$183.1111	$183.11	$183.10	$183.10
Purchase #4	$149.94	6.404%	$159.5422	$159.54	$159.55	$159.50
Purchase #5	$236.62	3.653%	$245.2637	$245.26	$245.25	$245.30
Purchase #6	$56.49	5.771%	$59.75	$59.75	$59.75	$59.80
Purchase #7	$73.29	12.643%	$82.5561	$82.56	$82.55	$82.60
7 purchase totals =	$1,038.08		$1,127.0811	$1,127.08	$1,127.05	$1,127.20