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	$168.37	4.306%	$175.62	$175.62	$175.60	$175.60
Purchase #2	$178.44	4.750%	$186.9159	$186.92	$186.90	$186.90
Purchase #3	$33.99	13.524%	$38.5868	$38.59	$38.60	$38.60
Purchase #4	$244.48	6.144%	$259.5009	$259.50	$259.50	$259.50
Purchase #5	$211.72	5.137%	$222.5961	$222.60	$222.60	$222.60
Purchase #6	$100.78	8.208%	$109.052	$109.05	$109.05	$109.10
Purchase #7	$14.88	10.773%	$16.483	$16.48	$16.50	$16.50
7 purchase totals =	$952.66		$1,008.7547	$1,008.76	$1,008.75	$1,008.80