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	$180.39	10.793%	$199.8595	$199.86	$199.85	$199.90
Purchase #2	$154.33	11.454%	$172.007	$172.01	$172.00	$172.00
Purchase #3	$140.71	7.500%	$151.2633	$151.26	$151.25	$151.30
Purchase #4	$190.28	12.230%	$213.5512	$213.55	$213.55	$213.60
Purchase #5	$155.82	10.179%	$171.6809	$171.68	$171.70	$171.70
Purchase #6	$131.95	6.765%	$140.8764	$140.88	$140.90	$140.90
Purchase #7	$16.45	7.257%	$17.6438	$17.64	$17.65	$17.60
7 purchase totals =	$969.93		$1,066.8821	$1,066.88	$1,066.90	$1,067.00