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	$107.32	4.375%	$112.0153	$112.02	$112.00	$112.00
Purchase #2	$190.83	9.526%	$209.0085	$209.01	$209.00	$209.00
Purchase #3	$89.26	12.113%	$100.0721	$100.07	$100.05	$100.10
Purchase #4	$239.55	6.817%	$255.8801	$255.88	$255.90	$255.90
Purchase #5	$162.40	6.140%	$172.3714	$172.37	$172.35	$172.40
Purchase #6	$135.91	4.215%	$141.6386	$141.64	$141.65	$141.60
Purchase #7	$206.66	13.315%	$234.1768	$234.18	$234.20	$234.20
7 purchase totals =	$1,131.93		$1,225.1628	$1,225.17	$1,225.15	$1,225.20