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	$174.32	6.540%	$185.7205	$185.72	$185.70	$185.70
Purchase #2	$186.93	5.373%	$196.9737	$196.97	$196.95	$197.00
Purchase #3	$247.57	12.846%	$279.3728	$279.37	$279.35	$279.40
Purchase #4	$91.92	13.478%	$104.309	$104.31	$104.30	$104.30
Purchase #5	$39.64	6.149%	$42.0775	$42.08	$42.10	$42.10
Purchase #6	$152.71	10.549%	$168.8194	$168.82	$168.80	$168.80
Purchase #7	$112.70	13.583%	$128.008	$128.01	$128.00	$128.00
7 purchase totals =	$1,005.79		$1,105.2809	$1,105.28	$1,105.20	$1,105.30