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	$69.75	5.610%	$73.663	$73.66	$73.65	$73.70
Purchase #2	$51.43	12.554%	$57.8865	$57.89	$57.90	$57.90
Purchase #3	$241.64	9.855%	$265.4536	$265.45	$265.45	$265.50
Purchase #4	$89.56	7.695%	$96.4516	$96.45	$96.45	$96.50
Purchase #5	$230.65	4.865%	$241.8711	$241.87	$241.85	$241.90
Purchase #6	$6.28	4.327%	$6.5517	$6.55	$6.55	$6.60
Purchase #7	$166.38	10.828%	$184.3956	$184.40	$184.40	$184.40
7 purchase totals =	$855.69		$926.2731	$926.27	$926.25	$926.50