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	$121.43	5.250%	$127.8051	$127.81	$127.80	$127.80
Purchase #2	$170.68	5.572%	$180.1903	$180.19	$180.20	$180.20
Purchase #3	$148.86	13.820%	$169.4325	$169.43	$169.45	$169.40
Purchase #4	$133.59	9.816%	$146.7032	$146.70	$146.70	$146.70
Purchase #5	$118.89	3.843%	$123.4589	$123.46	$123.45	$123.50
Purchase #6	$204.98	4.365%	$213.9274	$213.93	$213.95	$213.90
Purchase #7	$42.61	9.620%	$46.7091	$46.71	$46.70	$46.70
7 purchase totals =	$941.04		$1,008.2265	$1,008.23	$1,008.25	$1,008.20