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	$92.56	11.374%	$103.0878	$103.09	$103.10	$103.10
Purchase #2	$72.94	4.793%	$76.436	$76.44	$76.45	$76.40
Purchase #3	$156.98	8.389%	$170.1491	$170.15	$170.15	$170.10
Purchase #4	$225.45	13.195%	$255.1981	$255.20	$255.20	$255.20
Purchase #5	$143.37	11.267%	$159.5235	$159.52	$159.50	$159.50
Purchase #6	$227.38	12.516%	$255.8389	$255.84	$255.85	$255.80
Purchase #7	$90.54	9.399%	$99.0499	$99.05	$99.05	$99.00
7 purchase totals =	$1,009.22		$1,119.2833	$1,119.29	$1,119.30	$1,119.10