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	$239.54	9.735%	$262.8592	$262.86	$262.85	$262.90
Purchase #2	$136.64	13.782%	$155.4717	$155.47	$155.45	$155.50
Purchase #3	$203.96	3.262%	$210.6132	$210.61	$210.60	$210.60
Purchase #4	$89.77	7.358%	$96.3753	$96.38	$96.40	$96.40
Purchase #5	$90.90	5.585%	$95.9768	$95.98	$96.00	$96.00
Purchase #6	$175.82	8.160%	$190.1669	$190.17	$190.15	$190.20
Purchase #7	$191.79	12.780%	$216.3008	$216.30	$216.30	$216.30
7 purchase totals =	$1,128.42		$1,227.7639	$1,227.77	$1,227.75	$1,227.90