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	$82.25	6.196%	$87.3462	$87.35	$87.35	$87.30
Purchase #2	$180.46	8.597%	$195.9741	$195.97	$195.95	$196.00
Purchase #3	$89.61	10.845%	$99.3282	$99.33	$99.35	$99.30
Purchase #4	$84.32	4.220%	$87.8783	$87.88	$87.90	$87.90
Purchase #5	$91.38	3.521%	$94.5975	$94.60	$94.60	$94.60
Purchase #6	$89.95	7.324%	$96.5379	$96.54	$96.55	$96.50
Purchase #7	$58.85	4.675%	$61.6012	$61.60	$61.60	$61.60
7 purchase totals =	$676.82		$723.2634	$723.27	$723.30	$723.20