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	$61.69	4.715%	$64.5987	$64.60	$64.60	$64.60
Purchase #2	$135.92	11.254%	$151.2164	$151.22	$151.20	$151.20
Purchase #3	$82.93	10.400%	$91.5547	$91.55	$91.55	$91.60
Purchase #4	$105.65	11.234%	$117.5187	$117.52	$117.50	$117.50
Purchase #5	$241.59	6.777%	$257.9626	$257.96	$257.95	$258.00
Purchase #6	$152.50	12.616%	$171.7394	$171.74	$171.75	$171.70
Purchase #7	$150.49	9.661%	$165.0288	$165.03	$165.05	$165.00
7 purchase totals =	$930.77		$1,019.6193	$1,019.62	$1,019.60	$1,019.60