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	$205.90	13.252%	$233.1859	$233.19	$233.20	$233.20
Purchase #2	$56.32	4.544%	$58.8792	$58.88	$58.90	$58.90
Purchase #3	$209.87	9.491%	$229.7888	$229.79	$229.80	$229.80
Purchase #4	$175.50	9.674%	$192.4779	$192.48	$192.50	$192.50
Purchase #5	$85.80	5.777%	$90.7567	$90.76	$90.75	$90.80
Purchase #6	$172.90	12.771%	$194.9811	$194.98	$195.00	$195.00
Purchase #7	$90.40	11.292%	$100.608	$100.61	$100.60	$100.60
7 purchase totals =	$996.69		$1,100.6776	$1,100.69	$1,100.75	$1,100.80