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	$24.36	4.179%	$25.378	$25.38	$25.40	$25.40
Purchase #2	$162.55	5.840%	$172.0429	$172.04	$172.05	$172.00
Purchase #3	$245.90	6.525%	$261.945	$261.95	$261.95	$261.90
Purchase #4	$189.33	3.577%	$196.1023	$196.10	$196.10	$196.10
Purchase #5	$25.79	13.681%	$29.3183	$29.32	$29.30	$29.30
Purchase #6	$112.77	6.529%	$120.1328	$120.13	$120.15	$120.10
Purchase #7	$196.88	6.384%	$209.4488	$209.45	$209.45	$209.40
7 purchase totals =	$957.58		$1,014.3681	$1,014.37	$1,014.40	$1,014.20