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	$98.70	11.279%	$109.8324	$109.83	$109.85	$109.80
Purchase #2	$29.82	9.365%	$32.6126	$32.61	$32.60	$32.60
Purchase #3	$23.44	7.467%	$25.1903	$25.19	$25.20	$25.20
Purchase #4	$212.91	3.872%	$221.1539	$221.15	$221.15	$221.20
Purchase #5	$85.58	8.337%	$92.7148	$92.71	$92.70	$92.70
Purchase #6	$146.99	13.264%	$166.4868	$166.49	$166.50	$166.50
Purchase #7	$112.57	9.745%	$123.5399	$123.54	$123.55	$123.50
7 purchase totals =	$710.01		$771.5307	$771.52	$771.55	$771.50