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	$90.31	5.529%	$95.3032	$95.30	$95.30	$95.30
Purchase #2	$207.90	12.265%	$233.3989	$233.40	$233.40	$233.40
Purchase #3	$71.69	11.201%	$79.72	$79.72	$79.70	$79.70
Purchase #4	$243.36	6.185%	$258.4118	$258.41	$258.40	$258.40
Purchase #5	$83.91	12.531%	$94.4248	$94.42	$94.40	$94.40
Purchase #6	$32.67	7.587%	$35.1487	$35.15	$35.15	$35.10
Purchase #7	$202.54	6.443%	$215.5897	$215.59	$215.60	$215.60
7 purchase totals =	$932.38		$1,011.9971	$1,011.99	$1,011.95	$1,011.90