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	$145.33	4.596%	$152.0094	$152.01	$152.00	$152.00
Purchase #2	$107.48	3.443%	$111.1805	$111.18	$111.20	$111.20
Purchase #3	$116.83	9.739%	$128.2081	$128.21	$128.20	$128.20
Purchase #4	$78.81	8.476%	$85.4899	$85.49	$85.50	$85.50
Purchase #5	$108.96	4.751%	$114.1367	$114.14	$114.15	$114.10
Purchase #6	$29.59	12.868%	$33.3976	$33.40	$33.40	$33.40
Purchase #7	$191.92	9.661%	$210.4614	$210.46	$210.45	$210.50
7 purchase totals =	$778.92		$834.8836	$834.89	$834.90	$834.90