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	$88.33	8.745%	$96.0545	$96.05	$96.05	$96.10
Purchase #2	$218.30	5.591%	$230.5052	$230.51	$230.50	$230.50
Purchase #3	$93.91	4.847%	$98.4618	$98.46	$98.45	$98.50
Purchase #4	$92.59	11.508%	$103.2453	$103.25	$103.25	$103.20
Purchase #5	$100.37	13.335%	$113.7543	$113.75	$113.75	$113.80
Purchase #6	$61.71	9.847%	$67.7866	$67.79	$67.80	$67.80
Purchase #7	$181.32	8.536%	$196.7975	$196.80	$196.80	$196.80
7 purchase totals =	$836.53		$906.6052	$906.61	$906.60	$906.70