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	$127.78	7.690%	$137.6063	$137.61	$137.60	$137.60
Purchase #2	$199.63	9.684%	$218.9622	$218.96	$218.95	$219.00
Purchase #3	$38.45	6.836%	$41.0784	$41.08	$41.10	$41.10
Purchase #4	$98.56	11.316%	$109.713	$109.71	$109.70	$109.70
Purchase #5	$161.47	9.172%	$176.28	$176.28	$176.30	$176.30
Purchase #6	$130.65	5.136%	$137.3602	$137.36	$137.35	$137.40
Purchase #7	$219.90	9.174%	$240.0736	$240.07	$240.05	$240.10
7 purchase totals =	$976.44		$1,061.0737	$1,061.07	$1,061.05	$1,061.20