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	$187.32	12.734%	$211.1733	$211.17	$211.15	$211.20
Purchase #2	$19.80	10.659%	$21.9105	$21.91	$21.90	$21.90
Purchase #3	$82.56	11.321%	$91.9066	$91.91	$91.90	$91.90
Purchase #4	$177.69	8.547%	$192.8772	$192.88	$192.90	$192.90
Purchase #5	$74.28	10.721%	$82.2436	$82.24	$82.25	$82.20
Purchase #6	$227.40	6.668%	$242.563	$242.56	$242.55	$242.60
Purchase #7	$135.34	6.533%	$144.1818	$144.18	$144.20	$144.20
7 purchase totals =	$904.39		$986.8560	$986.85	$986.85	$986.90