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	$130.87	12.644%	$147.4172	$147.42	$147.40	$147.40
Purchase #2	$155.31	6.212%	$164.9579	$164.96	$164.95	$165.00
Purchase #3	$68.65	3.513%	$71.0617	$71.06	$71.05	$71.10
Purchase #4	$105.35	10.858%	$116.7889	$116.79	$116.80	$116.80
Purchase #5	$93.76	10.746%	$103.8354	$103.84	$103.85	$103.80
Purchase #6	$123.80	10.167%	$136.3867	$136.39	$136.40	$136.40
Purchase #7	$33.59	8.508%	$36.4478	$36.45	$36.45	$36.40
7 purchase totals =	$711.33		$776.8956	$776.91	$776.90	$776.90