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	$58.86	7.828%	$63.4676	$63.47	$63.45	$63.50
Purchase #2	$212.38	11.499%	$236.8016	$236.80	$236.80	$236.80
Purchase #3	$68.53	11.537%	$76.4363	$76.44	$76.45	$76.40
Purchase #4	$99.89	9.732%	$109.6113	$109.61	$109.60	$109.60
Purchase #5	$44.58	9.872%	$48.9809	$48.98	$49.00	$49.00
Purchase #6	$83.67	6.500%	$89.1086	$89.11	$89.10	$89.10
Purchase #7	$152.57	12.160%	$171.1225	$171.12	$171.10	$171.10
7 purchase totals =	$720.48		$795.5288	$795.53	$795.50	$795.50