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	$64.39	11.506%	$71.7987	$71.80	$71.80	$71.80
Purchase #2	$179.92	11.690%	$200.9526	$200.95	$200.95	$201.00
Purchase #3	$183.57	13.338%	$208.0546	$208.05	$208.05	$208.10
Purchase #4	$82.98	8.294%	$89.8624	$89.86	$89.85	$89.90
Purchase #5	$46.38	9.508%	$50.7898	$50.79	$50.80	$50.80
Purchase #6	$144.42	10.194%	$159.1422	$159.14	$159.15	$159.10
Purchase #7	$216.59	6.108%	$229.8193	$229.82	$229.80	$229.80
7 purchase totals =	$918.25		$1,010.4196	$1,010.41	$1,010.40	$1,010.50