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	$91.90	7.253%	$98.5655	$98.57	$98.55	$98.60
Purchase #2	$137.43	3.427%	$142.1397	$142.14	$142.15	$142.10
Purchase #3	$205.74	10.250%	$226.8284	$226.83	$226.85	$226.80
Purchase #4	$67.89	6.451%	$72.2696	$72.27	$72.25	$72.30
Purchase #5	$201.61	5.733%	$213.1683	$213.17	$213.15	$213.20
Purchase #6	$47.77	11.449%	$53.2392	$53.24	$53.25	$53.20
Purchase #7	$234.60	10.678%	$259.6506	$259.65	$259.65	$259.70
7 purchase totals =	$986.94		$1,065.8613	$1,065.87	$1,065.85	$1,065.90