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	$182.98	13.733%	$208.1086	$208.11	$208.10	$208.10
Purchase #2	$154.63	8.581%	$167.8988	$167.90	$167.90	$167.90
Purchase #3	$207.57	11.704%	$231.864	$231.86	$231.85	$231.90
Purchase #4	$94.90	3.792%	$98.4986	$98.50	$98.50	$98.50
Purchase #5	$82.25	9.738%	$90.2595	$90.26	$90.25	$90.30
Purchase #6	$250.74	5.695%	$265.0196	$265.02	$265.00	$265.00
Purchase #7	$171.84	11.314%	$191.282	$191.28	$191.30	$191.30
7 purchase totals =	$1,144.91		$1,252.9311	$1,252.93	$1,252.90	$1,253.00