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	$86.51	3.851%	$89.8415	$89.84	$89.85	$89.80
Purchase #2	$238.34	4.756%	$249.6755	$249.68	$249.70	$249.70
Purchase #3	$38.90	3.638%	$40.3152	$40.32	$40.30	$40.30
Purchase #4	$156.50	12.839%	$176.593	$176.59	$176.60	$176.60
Purchase #5	$248.81	7.761%	$268.1201	$268.12	$268.10	$268.10
Purchase #6	$200.75	10.802%	$222.435	$222.44	$222.45	$222.40
Purchase #7	$166.84	8.242%	$180.591	$180.59	$180.60	$180.60
7 purchase totals =	$1,136.65		$1,227.5713	$1,227.58	$1,227.60	$1,227.50