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	$182.77	5.707%	$193.2007	$193.20	$193.20	$193.20
Purchase #2	$77.53	7.400%	$83.2672	$83.27	$83.25	$83.30
Purchase #3	$133.90	11.715%	$149.5864	$149.59	$149.60	$149.60
Purchase #4	$65.38	9.654%	$71.6918	$71.69	$71.70	$71.70
Purchase #5	$113.93	12.640%	$128.3308	$128.33	$128.35	$128.30
Purchase #6	$85.83	5.337%	$90.4107	$90.41	$90.40	$90.40
Purchase #7	$98.85	7.125%	$105.8931	$105.89	$105.90	$105.90
7 purchase totals =	$758.19		$822.3807	$822.38	$822.40	$822.40