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	$220.64	4.661%	$230.924	$230.92	$230.90	$230.90
Purchase #2	$52.73	12.372%	$59.2538	$59.25	$59.25	$59.30
Purchase #3	$36.54	10.211%	$40.2711	$40.27	$40.25	$40.30
Purchase #4	$184.43	6.603%	$196.6079	$196.61	$196.60	$196.60
Purchase #5	$47.45	8.186%	$51.3343	$51.33	$51.35	$51.30
Purchase #6	$238.34	3.143%	$245.831	$245.83	$245.85	$245.80
Purchase #7	$99.64	3.671%	$103.2978	$103.30	$103.30	$103.30
7 purchase totals =	$879.77		$927.5199	$927.51	$927.50	$927.50