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	$106.27	12.738%	$119.8067	$119.81	$119.80	$119.80
Purchase #2	$130.27	8.642%	$141.5279	$141.53	$141.55	$141.50
Purchase #3	$51.81	7.822%	$55.8626	$55.86	$55.85	$55.90
Purchase #4	$183.92	6.687%	$196.2187	$196.22	$196.20	$196.20
Purchase #5	$18.50	3.460%	$19.1401	$19.14	$19.15	$19.10
Purchase #6	$133.57	9.434%	$146.171	$146.17	$146.15	$146.20
Purchase #7	$133.26	7.242%	$142.9107	$142.91	$142.90	$142.90
7 purchase totals =	$757.60		$821.6377	$821.64	$821.60	$821.60