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	$102.79	13.706%	$116.8784	$116.88	$116.90	$116.90
Purchase #2	$237.67	12.413%	$267.172	$267.17	$267.15	$267.20
Purchase #3	$73.56	12.231%	$82.5571	$82.56	$82.55	$82.60
Purchase #4	$182.31	3.328%	$188.3773	$188.38	$188.40	$188.40
Purchase #5	$131.65	4.247%	$137.2412	$137.24	$137.25	$137.20
Purchase #6	$143.46	8.306%	$155.3758	$155.38	$155.40	$155.40
Purchase #7	$148.87	4.598%	$155.715	$155.72	$155.70	$155.70
7 purchase totals =	$1,020.31		$1,103.3168	$1,103.33	$1,103.35	$1,103.40