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	$196.34	3.468%	$203.1491	$203.15	$203.15	$203.10
Purchase #2	$63.31	4.779%	$66.3356	$66.34	$66.35	$66.30
Purchase #3	$78.80	5.862%	$83.4193	$83.42	$83.40	$83.40
Purchase #4	$43.29	12.254%	$48.5948	$48.59	$48.60	$48.60
Purchase #5	$154.39	3.432%	$159.6887	$159.69	$159.70	$159.70
Purchase #6	$107.42	4.343%	$112.0853	$112.09	$112.10	$112.10
Purchase #7	$247.34	8.812%	$269.1356	$269.14	$269.15	$269.10
7 purchase totals =	$890.89		$942.4084	$942.42	$942.45	$942.30