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	$237.96	11.113%	$264.4045	$264.40	$264.40	$264.40
Purchase #2	$52.99	8.536%	$57.5132	$57.51	$57.50	$57.50
Purchase #3	$131.35	10.194%	$144.7398	$144.74	$144.75	$144.70
Purchase #4	$41.82	9.166%	$45.6532	$45.65	$45.65	$45.70
Purchase #5	$130.82	10.476%	$144.5247	$144.52	$144.50	$144.50
Purchase #6	$218.56	13.689%	$248.4787	$248.48	$248.50	$248.50
Purchase #7	$162.33	13.120%	$183.6277	$183.63	$183.65	$183.60
7 purchase totals =	$975.83		$1,088.9418	$1,088.93	$1,088.95	$1,088.90