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	$63.70	5.418%	$67.1513	$67.15	$67.15	$67.20
Purchase #2	$98.81	11.492%	$110.1652	$110.17	$110.15	$110.20
Purchase #3	$185.59	7.850%	$200.1588	$200.16	$200.15	$200.20
Purchase #4	$208.33	3.831%	$216.3111	$216.31	$216.30	$216.30
Purchase #5	$46.80	7.199%	$50.1691	$50.17	$50.15	$50.20
Purchase #6	$109.72	11.330%	$122.1513	$122.15	$122.15	$122.20
Purchase #7	$224.69	11.392%	$250.2867	$250.29	$250.30	$250.30
7 purchase totals =	$937.64		$1,016.3935	$1,016.40	$1,016.35	$1,016.60