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	$127.79	3.502%	$132.2652	$132.27	$132.25	$132.30
Purchase #2	$177.53	5.387%	$187.0935	$187.09	$187.10	$187.10
Purchase #3	$191.68	13.787%	$218.1069	$218.11	$218.10	$218.10
Purchase #4	$37.98	11.478%	$42.3393	$42.34	$42.35	$42.30
Purchase #5	$188.94	5.463%	$199.2618	$199.26	$199.25	$199.30
Purchase #6	$217.70	7.175%	$233.32	$233.32	$233.30	$233.30
Purchase #7	$106.88	3.711%	$110.8463	$110.85	$110.85	$110.80
7 purchase totals =	$1,048.50		$1,123.2330	$1,123.24	$1,123.20	$1,123.20