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	$131.99	4.203%	$137.5375	$137.54	$137.55	$137.50
Purchase #2	$225.42	4.817%	$236.2785	$236.28	$236.30	$236.30
Purchase #3	$21.78	12.130%	$24.4219	$24.42	$24.40	$24.40
Purchase #4	$205.57	13.719%	$233.7721	$233.77	$233.75	$233.80
Purchase #5	$110.67	11.162%	$123.023	$123.02	$123.00	$123.00
Purchase #6	$192.85	3.779%	$200.1378	$200.14	$200.15	$200.10
Purchase #7	$100.34	9.535%	$109.9074	$109.91	$109.90	$109.90
7 purchase totals =	$988.62		$1,065.0782	$1,065.08	$1,065.05	$1,065.00