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	$13.28	3.776%	$13.7815	$13.78	$13.80	$13.80
Purchase #2	$137.27	4.288%	$143.1561	$143.16	$143.15	$143.20
Purchase #3	$93.30	11.478%	$104.009	$104.01	$104.00	$104.00
Purchase #4	$122.89	7.553%	$132.1719	$132.17	$132.15	$132.20
Purchase #5	$249.34	5.844%	$263.9114	$263.91	$263.90	$263.90
Purchase #6	$171.73	11.585%	$191.6249	$191.62	$191.60	$191.60
Purchase #7	$216.32	4.356%	$225.7429	$225.74	$225.75	$225.70
7 purchase totals =	$1,004.13		$1,074.3977	$1,074.39	$1,074.35	$1,074.40