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	$118.52	4.426%	$123.7657	$123.77	$123.75	$123.80
Purchase #2	$40.88	11.573%	$45.611	$45.61	$45.60	$45.60
Purchase #3	$246.84	4.477%	$257.891	$257.89	$257.90	$257.90
Purchase #4	$67.61	3.164%	$69.7492	$69.75	$69.75	$69.70
Purchase #5	$112.54	7.461%	$120.9366	$120.94	$120.95	$120.90
Purchase #6	$26.61	4.404%	$27.7819	$27.78	$27.80	$27.80
Purchase #7	$189.80	11.232%	$211.1183	$211.12	$211.10	$211.10
7 purchase totals =	$802.80		$856.8537	$856.86	$856.85	$856.80