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	$135.94	5.836%	$143.8735	$143.87	$143.85	$143.90
Purchase #2	$148.37	11.521%	$165.4637	$165.46	$165.45	$165.50
Purchase #3	$141.56	3.653%	$146.7312	$146.73	$146.75	$146.70
Purchase #4	$64.89	5.129%	$68.2182	$68.22	$68.20	$68.20
Purchase #5	$178.34	6.710%	$190.3066	$190.31	$190.30	$190.30
Purchase #6	$249.79	7.443%	$268.3819	$268.38	$268.40	$268.40
Purchase #7	$13.66	3.680%	$14.1627	$14.16	$14.15	$14.20
7 purchase totals =	$932.55		$997.1378	$997.13	$997.10	$997.20