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	$78.92	9.222%	$86.198	$86.20	$86.20	$86.20
Purchase #2	$249.48	5.412%	$262.9819	$262.98	$263.00	$263.00
Purchase #3	$179.58	9.695%	$196.9903	$196.99	$197.00	$197.00
Purchase #4	$168.61	3.517%	$174.54	$174.54	$174.55	$174.50
Purchase #5	$119.69	7.360%	$128.4992	$128.50	$128.50	$128.50
Purchase #6	$134.42	9.380%	$147.0286	$147.03	$147.05	$147.00
Purchase #7	$82.33	9.283%	$89.9727	$89.97	$89.95	$90.00
7 purchase totals =	$1,013.03		$1,086.2107	$1,086.21	$1,086.25	$1,086.20