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	$78.82	9.629%	$86.4096	$86.41	$86.40	$86.40
Purchase #2	$141.44	11.632%	$157.8923	$157.89	$157.90	$157.90
Purchase #3	$185.87	5.857%	$196.7564	$196.76	$196.75	$196.80
Purchase #4	$195.43	5.268%	$205.7253	$205.73	$205.75	$205.70
Purchase #5	$83.76	10.702%	$92.724	$92.72	$92.70	$92.70
Purchase #6	$249.62	13.870%	$284.2423	$284.24	$284.25	$284.20
Purchase #7	$109.52	6.308%	$116.4285	$116.43	$116.45	$116.40
7 purchase totals =	$1,044.46		$1,140.1784	$1,140.18	$1,140.20	$1,140.10