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	$213.26	9.465%	$233.4451	$233.45	$233.45	$233.40
Purchase #2	$164.60	9.390%	$180.0559	$180.06	$180.05	$180.10
Purchase #3	$82.79	11.406%	$92.233	$92.23	$92.25	$92.20
Purchase #4	$12.73	12.482%	$14.319	$14.32	$14.30	$14.30
Purchase #5	$215.70	4.587%	$225.5942	$225.59	$225.60	$225.60
Purchase #6	$22.94	8.165%	$24.8131	$24.81	$24.80	$24.80
Purchase #7	$17.54	7.446%	$18.846	$18.85	$18.85	$18.80
7 purchase totals =	$729.56		$789.3063	$789.31	$789.30	$789.20