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	$133.57	10.317%	$147.3504	$147.35	$147.35	$147.40
Purchase #2	$104.33	7.500%	$112.1548	$112.15	$112.15	$112.20
Purchase #3	$79.90	12.508%	$89.8939	$89.89	$89.90	$89.90
Purchase #4	$208.93	3.874%	$217.0239	$217.02	$217.00	$217.00
Purchase #5	$171.93	9.138%	$187.641	$187.64	$187.65	$187.60
Purchase #6	$112.48	12.137%	$126.1317	$126.13	$126.15	$126.10
Purchase #7	$53.36	7.426%	$57.3225	$57.32	$57.30	$57.30
7 purchase totals =	$864.50		$937.5182	$937.50	$937.50	$937.50