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	$162.48	11.537%	$181.2253	$181.23	$181.25	$181.20
Purchase #2	$167.79	11.384%	$186.8912	$186.89	$186.90	$186.90
Purchase #3	$83.45	10.732%	$92.4059	$92.41	$92.40	$92.40
Purchase #4	$247.38	3.743%	$256.6394	$256.64	$256.65	$256.60
Purchase #5	$93.73	6.233%	$99.5722	$99.57	$99.55	$99.60
Purchase #6	$228.71	8.487%	$248.1206	$248.12	$248.10	$248.10
Purchase #7	$32.65	7.235%	$35.0122	$35.01	$35.00	$35.00
7 purchase totals =	$1,016.19		$1,099.8668	$1,099.87	$1,099.85	$1,099.80