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	$141.42	12.136%	$158.5827	$158.58	$158.60	$158.60
Purchase #2	$9.99	10.109%	$10.9999	$11.00	$11.00	$11.00
Purchase #3	$98.29	11.373%	$109.4685	$109.47	$109.45	$109.50
Purchase #4	$165.68	5.209%	$174.3103	$174.31	$174.30	$174.30
Purchase #5	$243.43	7.310%	$261.2247	$261.22	$261.20	$261.20
Purchase #6	$67.91	7.334%	$72.8905	$72.89	$72.90	$72.90
Purchase #7	$35.87	12.441%	$40.3326	$40.33	$40.35	$40.30
7 purchase totals =	$762.59		$827.8092	$827.80	$827.80	$827.80