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	$222.52	9.305%	$243.2255	$243.23	$243.25	$243.20
Purchase #2	$158.31	10.776%	$175.3695	$175.37	$175.35	$175.40
Purchase #3	$87.58	4.578%	$91.5894	$91.59	$91.60	$91.60
Purchase #4	$194.39	8.335%	$210.5924	$210.59	$210.60	$210.60
Purchase #5	$112.94	9.149%	$123.2729	$123.27	$123.25	$123.30
Purchase #6	$150.41	7.459%	$161.6291	$161.63	$161.65	$161.60
Purchase #7	$54.41	8.119%	$58.8275	$58.83	$58.85	$58.80
7 purchase totals =	$980.56		$1,064.5063	$1,064.51	$1,064.55	$1,064.50