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	$215.54	11.529%	$240.3896	$240.39	$240.40	$240.40
Purchase #2	$37.27	5.806%	$39.4339	$39.43	$39.45	$39.40
Purchase #3	$91.55	4.842%	$95.9829	$95.98	$96.00	$96.00
Purchase #4	$209.98	5.485%	$221.4974	$221.50	$221.50	$221.50
Purchase #5	$34.32	3.347%	$35.4687	$35.47	$35.45	$35.50
Purchase #6	$211.27	10.380%	$233.1998	$233.20	$233.20	$233.20
Purchase #7	$180.90	6.459%	$192.5843	$192.58	$192.60	$192.60
7 purchase totals =	$980.83		$1,058.5566	$1,058.55	$1,058.60	$1,058.60