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	$213.82	7.241%	$229.3027	$229.30	$229.30	$229.30
Purchase #2	$102.54	12.620%	$115.4805	$115.48	$115.50	$115.50
Purchase #3	$163.42	13.700%	$185.8085	$185.81	$185.80	$185.80
Purchase #4	$54.75	8.687%	$59.5061	$59.51	$59.50	$59.50
Purchase #5	$87.72	9.658%	$96.192	$96.19	$96.20	$96.20
Purchase #6	$208.70	3.365%	$215.7228	$215.72	$215.70	$215.70
Purchase #7	$161.38	9.313%	$176.4093	$176.41	$176.40	$176.40
7 purchase totals =	$992.33		$1,078.4219	$1,078.42	$1,078.40	$1,078.40