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	$94.71	6.215%	$100.5962	$100.60	$100.60	$100.60
Purchase #2	$46.93	12.723%	$52.9009	$52.90	$52.90	$52.90
Purchase #3	$50.95	7.410%	$54.7254	$54.73	$54.75	$54.70
Purchase #4	$158.75	11.257%	$176.6205	$176.62	$176.60	$176.60
Purchase #5	$236.28	3.315%	$244.1127	$244.11	$244.10	$244.10
Purchase #6	$194.39	6.121%	$206.2886	$206.29	$206.30	$206.30
Purchase #7	$37.53	4.595%	$39.2545	$39.25	$39.25	$39.30
7 purchase totals =	$819.54		$874.4988	$874.50	$874.50	$874.50