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	$162.28	5.828%	$171.7377	$171.74	$171.75	$171.70
Purchase #2	$167.34	5.541%	$176.6123	$176.61	$176.60	$176.60
Purchase #3	$87.27	11.684%	$97.4666	$97.47	$97.45	$97.50
Purchase #4	$66.83	5.196%	$70.3025	$70.30	$70.30	$70.30
Purchase #5	$116.96	12.444%	$131.5145	$131.51	$131.50	$131.50
Purchase #6	$220.43	9.506%	$241.3841	$241.38	$241.40	$241.40
Purchase #7	$96.76	6.753%	$103.2942	$103.29	$103.30	$103.30
7 purchase totals =	$917.87		$992.3119	$992.30	$992.30	$992.30