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	$215.40	5.792%	$227.876	$227.88	$227.90	$227.90
Purchase #2	$32.80	3.505%	$33.9496	$33.95	$33.95	$33.90
Purchase #3	$187.96	11.520%	$209.613	$209.61	$209.60	$209.60
Purchase #4	$162.74	13.758%	$185.1298	$185.13	$185.15	$185.10
Purchase #5	$242.49	8.308%	$262.6361	$262.64	$262.65	$262.60
Purchase #6	$91.43	3.122%	$94.2844	$94.28	$94.30	$94.30
Purchase #7	$100.95	11.236%	$112.2927	$112.29	$112.30	$112.30
7 purchase totals =	$1,033.77		$1,125.7816	$1,125.78	$1,125.85	$1,125.70