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	$59.54	5.831%	$63.0118	$63.01	$63.00	$63.00
Purchase #2	$42.91	9.310%	$46.9049	$46.90	$46.90	$46.90
Purchase #3	$190.25	3.834%	$197.5442	$197.54	$197.55	$197.50
Purchase #4	$131.81	11.433%	$146.8798	$146.88	$146.90	$146.90
Purchase #5	$170.97	12.246%	$191.907	$191.91	$191.90	$191.90
Purchase #6	$84.37	5.816%	$89.277	$89.28	$89.30	$89.30
Purchase #7	$56.74	3.227%	$58.571	$58.57	$58.55	$58.60
7 purchase totals =	$736.59		$794.0957	$794.09	$794.10	$794.10