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	$41.26	11.220%	$45.8894	$45.89	$45.90	$45.90
Purchase #2	$111.67	9.484%	$122.2608	$122.26	$122.25	$122.30
Purchase #3	$245.47	11.632%	$274.0231	$274.02	$274.00	$274.00
Purchase #4	$198.42	9.805%	$217.8751	$217.88	$217.90	$217.90
Purchase #5	$47.86	8.250%	$51.8085	$51.81	$51.80	$51.80
Purchase #6	$44.88	3.177%	$46.3058	$46.31	$46.30	$46.30
Purchase #7	$229.77	12.826%	$259.2403	$259.24	$259.25	$259.20
7 purchase totals =	$919.33		$1,017.4030	$1,017.41	$1,017.40	$1,017.40