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	$142.61	9.479%	$156.128	$156.13	$156.15	$156.10
Purchase #2	$138.86	6.283%	$147.5846	$147.58	$147.60	$147.60
Purchase #3	$85.34	6.786%	$91.1312	$91.13	$91.15	$91.10
Purchase #4	$117.78	11.461%	$131.2788	$131.28	$131.30	$131.30
Purchase #5	$22.31	11.646%	$24.9082	$24.91	$24.90	$24.90
Purchase #6	$159.66	4.449%	$166.7633	$166.76	$166.75	$166.80
Purchase #7	$243.25	7.783%	$262.1821	$262.18	$262.20	$262.20
7 purchase totals =	$909.81		$979.9762	$979.97	$980.05	$980.00