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	$106.37	3.342%	$109.9249	$109.92	$109.90	$109.90
Purchase #2	$25.83	13.291%	$29.2631	$29.26	$29.25	$29.30
Purchase #3	$244.38	13.816%	$278.1435	$278.14	$278.15	$278.10
Purchase #4	$16.77	12.121%	$18.8027	$18.80	$18.80	$18.80
Purchase #5	$56.28	9.480%	$61.6153	$61.62	$61.60	$61.60
Purchase #6	$17.81	13.559%	$20.2249	$20.22	$20.20	$20.20
Purchase #7	$160.39	9.476%	$175.5886	$175.59	$175.60	$175.60
7 purchase totals =	$627.83		$693.5630	$693.55	$693.50	$693.50