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	$48.25	9.328%	$52.7508	$52.75	$52.75	$52.80
Purchase #2	$178.30	3.127%	$183.8754	$183.88	$183.90	$183.90
Purchase #3	$37.26	4.501%	$38.9371	$38.94	$38.95	$38.90
Purchase #4	$155.69	8.816%	$169.4156	$169.42	$169.40	$169.40
Purchase #5	$155.48	11.140%	$172.8005	$172.80	$172.80	$172.80
Purchase #6	$86.27	11.436%	$96.1358	$96.14	$96.15	$96.10
Purchase #7	$153.26	10.208%	$168.9048	$168.90	$168.90	$168.90
7 purchase totals =	$814.51		$882.8200	$882.83	$882.85	$882.80