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	$198.56	7.206%	$212.8682	$212.87	$212.85	$212.90
Purchase #2	$110.86	11.117%	$123.1843	$123.18	$123.20	$123.20
Purchase #3	$140.88	4.622%	$147.3915	$147.39	$147.40	$147.40
Purchase #4	$216.34	5.687%	$228.6433	$228.64	$228.65	$228.60
Purchase #5	$79.54	4.126%	$82.8218	$82.82	$82.80	$82.80
Purchase #6	$130.62	8.197%	$141.3269	$141.33	$141.35	$141.30
Purchase #7	$180.42	3.591%	$186.8989	$186.90	$186.90	$186.90
7 purchase totals =	$1,057.22		$1,123.1349	$1,123.13	$1,123.15	$1,123.10