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	$10.51	7.497%	$11.2979	$11.30	$11.30	$11.30
Purchase #2	$160.49	11.462%	$178.8854	$178.89	$178.90	$178.90
Purchase #3	$216.89	13.250%	$245.6279	$245.63	$245.65	$245.60
Purchase #4	$57.63	6.779%	$61.5367	$61.54	$61.55	$61.50
Purchase #5	$138.77	10.802%	$153.7599	$153.76	$153.75	$153.80
Purchase #6	$207.36	10.575%	$229.2883	$229.29	$229.30	$229.30
Purchase #7	$126.80	8.195%	$137.1913	$137.19	$137.20	$137.20
7 purchase totals =	$918.45		$1,017.5874	$1,017.60	$1,017.65	$1,017.60