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	$52.59	8.840%	$57.239	$57.24	$57.25	$57.20
Purchase #2	$148.46	9.299%	$162.2653	$162.27	$162.25	$162.30
Purchase #3	$33.45	10.851%	$37.0797	$37.08	$37.10	$37.10
Purchase #4	$41.79	4.348%	$43.607	$43.61	$43.60	$43.60
Purchase #5	$74.47	3.149%	$76.8151	$76.82	$76.80	$76.80
Purchase #6	$155.50	4.803%	$162.9687	$162.97	$162.95	$163.00
Purchase #7	$220.29	3.651%	$228.3328	$228.33	$228.35	$228.30
7 purchase totals =	$726.55		$768.3076	$768.32	$768.30	$768.30