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	$58.29	10.791%	$64.5801	$64.58	$64.60	$64.60
Purchase #2	$32.88	10.419%	$36.3058	$36.31	$36.30	$36.30
Purchase #3	$113.26	4.364%	$118.2027	$118.20	$118.20	$118.20
Purchase #4	$35.92	4.309%	$37.4678	$37.47	$37.45	$37.50
Purchase #5	$13.54	4.782%	$14.1875	$14.19	$14.20	$14.20
Purchase #6	$158.46	6.359%	$168.5365	$168.54	$168.55	$168.50
Purchase #7	$52.86	11.609%	$58.9965	$59.00	$59.00	$59.00
7 purchase totals =	$465.21		$498.2769	$498.29	$498.30	$498.30