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	$67.96	6.758%	$72.5527	$72.55	$72.55	$72.60
Purchase #2	$185.45	7.677%	$199.687	$199.69	$199.70	$199.70
Purchase #3	$153.29	9.503%	$167.8571	$167.86	$167.85	$167.90
Purchase #4	$231.76	3.530%	$239.9411	$239.94	$239.95	$239.90
Purchase #5	$63.76	12.699%	$71.8569	$71.86	$71.85	$71.90
Purchase #6	$81.36	6.712%	$86.8209	$86.82	$86.80	$86.80
Purchase #7	$249.60	11.690%	$278.7782	$278.78	$278.80	$278.80
7 purchase totals =	$1,033.18		$1,117.4939	$1,117.50	$1,117.50	$1,117.60