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	$125.53	5.387%	$132.2923	$132.29	$132.30	$132.30
Purchase #2	$204.79	7.640%	$220.436	$220.44	$220.45	$220.40
Purchase #3	$233.33	12.706%	$262.9769	$262.98	$263.00	$263.00
Purchase #4	$108.40	3.859%	$112.5832	$112.58	$112.60	$112.60
Purchase #5	$33.30	5.320%	$35.0716	$35.07	$35.05	$35.10
Purchase #6	$212.83	12.483%	$239.3976	$239.40	$239.40	$239.40
Purchase #7	$52.87	11.641%	$59.0246	$59.02	$59.00	$59.00
7 purchase totals =	$971.05		$1,061.7822	$1,061.78	$1,061.80	$1,061.80