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	$234.82	12.222%	$263.5197	$263.52	$263.50	$263.50
Purchase #2	$67.43	8.774%	$73.3463	$73.35	$73.35	$73.30
Purchase #3	$56.95	12.648%	$64.153	$64.15	$64.15	$64.20
Purchase #4	$112.95	13.363%	$128.0435	$128.04	$128.05	$128.00
Purchase #5	$114.85	13.290%	$130.1136	$130.11	$130.10	$130.10
Purchase #6	$176.39	5.781%	$186.5871	$186.59	$186.60	$186.60
Purchase #7	$121.48	5.309%	$127.9294	$127.93	$127.95	$127.90
7 purchase totals =	$884.87		$973.6926	$973.69	$973.70	$973.60