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	$152.27	9.451%	$166.661	$166.66	$166.65	$166.70
Purchase #2	$125.71	4.735%	$131.6624	$131.66	$131.65	$131.70
Purchase #3	$78.57	5.339%	$82.7649	$82.76	$82.75	$82.80
Purchase #4	$93.75	3.414%	$96.9506	$96.95	$96.95	$97.00
Purchase #5	$191.58	13.391%	$217.2345	$217.23	$217.25	$217.20
Purchase #6	$40.60	5.214%	$42.7169	$42.72	$42.70	$42.70
Purchase #7	$162.85	6.494%	$173.4255	$173.43	$173.45	$173.40
7 purchase totals =	$845.33		$911.4158	$911.41	$911.40	$911.50