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	$82.27	12.863%	$92.8524	$92.85	$92.85	$92.90
Purchase #2	$36.97	8.815%	$40.2289	$40.23	$40.25	$40.20
Purchase #3	$241.96	4.342%	$252.4659	$252.47	$252.45	$252.50
Purchase #4	$212.39	8.152%	$229.704	$229.70	$229.70	$229.70
Purchase #5	$55.28	9.345%	$60.4459	$60.45	$60.45	$60.40
Purchase #6	$241.80	11.498%	$269.6022	$269.60	$269.60	$269.60
Purchase #7	$54.46	9.589%	$59.6822	$59.68	$59.70	$59.70
7 purchase totals =	$925.13		$1,004.9815	$1,004.98	$1,005.00	$1,005.00