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	$88.58	9.235%	$96.7604	$96.76	$96.75	$96.80
Purchase #2	$18.31	10.404%	$20.215	$20.22	$20.20	$20.20
Purchase #3	$91.47	8.823%	$99.5404	$99.54	$99.55	$99.50
Purchase #4	$174.95	4.550%	$182.9102	$182.91	$182.90	$182.90
Purchase #5	$132.35	11.817%	$147.9898	$147.99	$148.00	$148.00
Purchase #6	$31.85	3.153%	$32.8542	$32.85	$32.85	$32.90
Purchase #7	$151.38	6.743%	$161.5876	$161.59	$161.60	$161.60
7 purchase totals =	$688.89		$741.8576	$741.86	$741.85	$741.90