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	$200.97	9.265%	$219.5899	$219.59	$219.60	$219.60
Purchase #2	$105.72	8.136%	$114.3214	$114.32	$114.30	$114.30
Purchase #3	$47.95	11.812%	$53.6139	$53.61	$53.60	$53.60
Purchase #4	$82.31	8.554%	$89.3508	$89.35	$89.35	$89.40
Purchase #5	$243.72	7.428%	$261.8235	$261.82	$261.80	$261.80
Purchase #6	$218.82	13.612%	$248.6058	$248.61	$248.60	$248.60
Purchase #7	$118.79	8.652%	$129.0677	$129.07	$129.05	$129.10
7 purchase totals =	$1,018.28		$1,116.3730	$1,116.37	$1,116.30	$1,116.40