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	$163.34	13.726%	$185.76	$185.76	$185.75	$185.80
Purchase #2	$55.78	8.425%	$60.4795	$60.48	$60.50	$60.50
Purchase #3	$114.64	8.385%	$124.2526	$124.25	$124.25	$124.30
Purchase #4	$179.65	13.276%	$203.5003	$203.50	$203.50	$203.50
Purchase #5	$75.59	13.465%	$85.7682	$85.77	$85.75	$85.80
Purchase #6	$55.86	6.724%	$59.616	$59.62	$59.60	$59.60
Purchase #7	$198.97	11.232%	$221.3183	$221.32	$221.30	$221.30
7 purchase totals =	$843.83		$940.6949	$940.70	$940.65	$940.80