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	$155.97	10.154%	$171.8072	$171.81	$171.80	$171.80
Purchase #2	$79.86	4.275%	$83.274	$83.27	$83.25	$83.30
Purchase #3	$88.47	3.778%	$91.8124	$91.81	$91.80	$91.80
Purchase #4	$64.91	8.402%	$70.3637	$70.36	$70.35	$70.40
Purchase #5	$245.68	4.371%	$256.4187	$256.42	$256.40	$256.40
Purchase #6	$94.58	3.294%	$97.6955	$97.70	$97.70	$97.70
Purchase #7	$222.39	11.709%	$248.4296	$248.43	$248.45	$248.40
7 purchase totals =	$951.86		$1,019.8011	$1,019.80	$1,019.75	$1,019.80