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	$67.34	5.655%	$71.1481	$71.15	$71.15	$71.10
Purchase #2	$112.58	9.723%	$123.5262	$123.53	$123.55	$123.50
Purchase #3	$159.74	3.127%	$164.7351	$164.74	$164.75	$164.70
Purchase #4	$196.91	8.354%	$213.3599	$213.36	$213.35	$213.40
Purchase #5	$222.83	9.370%	$243.7092	$243.71	$243.70	$243.70
Purchase #6	$35.71	12.574%	$40.2002	$40.20	$40.20	$40.20
Purchase #7	$184.96	10.775%	$204.8894	$204.89	$204.90	$204.90
7 purchase totals =	$980.07		$1,061.5681	$1,061.58	$1,061.60	$1,061.50