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	$244.69	11.766%	$273.4802	$273.48	$273.50	$273.50
Purchase #2	$16.33	6.223%	$17.3462	$17.35	$17.35	$17.30
Purchase #3	$119.57	9.515%	$130.9471	$130.95	$130.95	$130.90
Purchase #4	$172.91	10.720%	$191.446	$191.45	$191.45	$191.40
Purchase #5	$131.27	10.630%	$145.224	$145.22	$145.20	$145.20
Purchase #6	$183.72	10.681%	$203.3431	$203.34	$203.35	$203.30
Purchase #7	$50.92	6.560%	$54.2604	$54.26	$54.25	$54.30
7 purchase totals =	$919.41		$1,016.0470	$1,016.05	$1,016.05	$1,015.90