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	$32.40	5.159%	$34.0715	$34.07	$34.05	$34.10
Purchase #2	$242.76	5.312%	$255.6554	$255.66	$255.65	$255.70
Purchase #3	$55.79	9.642%	$61.1693	$61.17	$61.15	$61.20
Purchase #4	$199.74	11.767%	$223.2434	$223.24	$223.25	$223.20
Purchase #5	$127.74	3.656%	$132.4102	$132.41	$132.40	$132.40
Purchase #6	$123.75	5.561%	$130.6317	$130.63	$130.65	$130.60
Purchase #7	$228.27	7.395%	$245.1506	$245.15	$245.15	$245.20
7 purchase totals =	$1,010.45		$1,082.3321	$1,082.33	$1,082.30	$1,082.40