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	$39.40	10.820%	$43.6631	$43.66	$43.65	$43.70
Purchase #2	$158.36	4.278%	$165.1346	$165.13	$165.15	$165.10
Purchase #3	$85.36	13.596%	$96.9655	$96.97	$96.95	$97.00
Purchase #4	$105.68	3.638%	$109.5246	$109.52	$109.50	$109.50
Purchase #5	$82.42	4.356%	$86.0102	$86.01	$86.00	$86.00
Purchase #6	$182.71	7.806%	$196.9723	$196.97	$196.95	$197.00
Purchase #7	$20.38	12.277%	$22.8821	$22.88	$22.90	$22.90
7 purchase totals =	$674.31		$721.1524	$721.14	$721.10	$721.20