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	$150.47	9.850%	$165.2913	$165.29	$165.30	$165.30
Purchase #2	$20.67	5.669%	$21.8418	$21.84	$21.85	$21.80
Purchase #3	$30.31	11.154%	$33.6908	$33.69	$33.70	$33.70
Purchase #4	$32.82	8.784%	$35.7029	$35.70	$35.70	$35.70
Purchase #5	$30.94	5.329%	$32.5888	$32.59	$32.60	$32.60
Purchase #6	$38.63	12.164%	$43.329	$43.33	$43.35	$43.30
Purchase #7	$63.92	6.416%	$68.0211	$68.02	$68.00	$68.00
7 purchase totals =	$367.76		$400.4657	$400.46	$400.50	$400.40