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	$67.93	5.463%	$71.641	$71.64	$71.65	$71.60
Purchase #2	$164.47	9.651%	$180.343	$180.34	$180.35	$180.30
Purchase #3	$139.64	11.553%	$155.7726	$155.77	$155.75	$155.80
Purchase #4	$81.64	11.327%	$90.8874	$90.89	$90.90	$90.90
Purchase #5	$209.37	4.404%	$218.5907	$218.59	$218.60	$218.60
Purchase #6	$137.50	9.227%	$150.1871	$150.19	$150.20	$150.20
Purchase #7	$57.29	4.684%	$59.9735	$59.97	$59.95	$60.00
7 purchase totals =	$857.84		$927.3953	$927.39	$927.40	$927.40