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	$217.93	10.316%	$240.4117	$240.41	$240.40	$240.40
Purchase #2	$195.78	9.731%	$214.8314	$214.83	$214.85	$214.80
Purchase #3	$156.80	7.219%	$168.1194	$168.12	$168.10	$168.10
Purchase #4	$33.52	6.339%	$35.6448	$35.64	$35.65	$35.60
Purchase #5	$94.66	3.691%	$98.1539	$98.15	$98.15	$98.20
Purchase #6	$62.67	4.191%	$65.2965	$65.30	$65.30	$65.30
Purchase #7	$162.76	5.144%	$171.1324	$171.13	$171.15	$171.10
7 purchase totals =	$924.12		$993.5901	$993.58	$993.60	$993.50