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	$81.81	9.667%	$89.7186	$89.72	$89.70	$89.70
Purchase #2	$210.31	5.308%	$221.4733	$221.47	$221.45	$221.50
Purchase #3	$5.43	8.691%	$5.9019	$5.90	$5.90	$5.90
Purchase #4	$198.42	11.619%	$221.4744	$221.47	$221.45	$221.50
Purchase #5	$39.58	13.798%	$45.0412	$45.04	$45.05	$45.00
Purchase #6	$218.62	8.755%	$237.7602	$237.76	$237.75	$237.80
Purchase #7	$188.69	8.554%	$204.8305	$204.83	$204.85	$204.80
7 purchase totals =	$942.86		$1,026.2001	$1,026.19	$1,026.15	$1,026.20