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	$78.75	9.812%	$86.477	$86.48	$86.50	$86.50
Purchase #2	$226.80	6.492%	$241.5239	$241.52	$241.50	$241.50
Purchase #3	$14.89	13.262%	$16.8647	$16.86	$16.85	$16.90
Purchase #4	$113.54	12.505%	$127.7382	$127.74	$127.75	$127.70
Purchase #5	$17.69	11.492%	$19.7229	$19.72	$19.70	$19.70
Purchase #6	$123.53	13.276%	$139.9298	$139.93	$139.95	$139.90
Purchase #7	$89.66	9.693%	$98.3507	$98.35	$98.35	$98.40
7 purchase totals =	$664.86		$730.6072	$730.60	$730.60	$730.60