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	$69.38	10.395%	$76.5921	$76.59	$76.60	$76.60
Purchase #2	$72.70	13.827%	$82.7522	$82.75	$82.75	$82.80
Purchase #3	$48.49	3.660%	$50.2647	$50.26	$50.25	$50.30
Purchase #4	$242.83	12.621%	$273.4776	$273.48	$273.50	$273.50
Purchase #5	$147.29	11.705%	$164.5303	$164.53	$164.55	$164.50
Purchase #6	$221.60	10.669%	$245.2425	$245.24	$245.25	$245.20
Purchase #7	$28.27	4.121%	$29.435	$29.44	$29.45	$29.40
7 purchase totals =	$830.56		$922.2944	$922.29	$922.35	$922.30