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	$149.30	10.694%	$165.2661	$165.27	$165.25	$165.30
Purchase #2	$188.61	8.533%	$204.7041	$204.70	$204.70	$204.70
Purchase #3	$141.75	6.811%	$151.4046	$151.40	$151.40	$151.40
Purchase #4	$194.49	7.237%	$208.5652	$208.57	$208.55	$208.60
Purchase #5	$132.95	7.398%	$142.7856	$142.79	$142.80	$142.80
Purchase #6	$102.96	6.437%	$109.5875	$109.59	$109.60	$109.60
Purchase #7	$95.77	5.419%	$100.9598	$100.96	$100.95	$101.00
7 purchase totals =	$1,005.83		$1,083.2729	$1,083.28	$1,083.25	$1,083.40