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	$230.61	4.549%	$241.1004	$241.10	$241.10	$241.10
Purchase #2	$35.78	12.674%	$40.3148	$40.31	$40.30	$40.30
Purchase #3	$99.56	11.829%	$111.337	$111.34	$111.35	$111.30
Purchase #4	$235.90	10.386%	$260.4006	$260.40	$260.40	$260.40
Purchase #5	$206.25	4.524%	$215.5808	$215.58	$215.60	$215.60
Purchase #6	$110.53	7.109%	$118.3876	$118.39	$118.40	$118.40
Purchase #7	$47.58	8.250%	$51.5054	$51.51	$51.50	$51.50
7 purchase totals =	$966.21		$1,038.6266	$1,038.63	$1,038.65	$1,038.60