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	$233.47	5.562%	$246.4556	$246.46	$246.45	$246.50
Purchase #2	$209.26	12.727%	$235.8925	$235.89	$235.90	$235.90
Purchase #3	$68.98	5.132%	$72.5201	$72.52	$72.50	$72.50
Purchase #4	$37.73	12.772%	$42.5489	$42.55	$42.55	$42.50
Purchase #5	$189.55	8.698%	$206.0371	$206.04	$206.05	$206.00
Purchase #6	$219.67	5.373%	$231.4729	$231.47	$231.45	$231.50
Purchase #7	$106.80	12.499%	$120.1489	$120.15	$120.15	$120.10
7 purchase totals =	$1,065.46		$1,155.0760	$1,155.08	$1,155.05	$1,155.00