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	$167.98	4.450%	$175.4551	$175.46	$175.45	$175.50
Purchase #2	$76.68	13.179%	$86.7857	$86.79	$86.80	$86.80
Purchase #3	$128.47	13.238%	$145.4769	$145.48	$145.50	$145.50
Purchase #4	$94.27	12.794%	$106.3309	$106.33	$106.35	$106.30
Purchase #5	$198.29	8.287%	$214.7223	$214.72	$214.70	$214.70
Purchase #6	$35.59	5.556%	$37.5674	$37.57	$37.55	$37.60
Purchase #7	$221.61	3.157%	$228.6062	$228.61	$228.60	$228.60
7 purchase totals =	$922.89		$994.9445	$994.96	$994.95	$995.00