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	$186.33	7.126%	$199.6079	$199.61	$199.60	$199.60
Purchase #2	$102.89	13.451%	$116.7297	$116.73	$116.75	$116.70
Purchase #3	$119.98	7.202%	$128.621	$128.62	$128.60	$128.60
Purchase #4	$39.98	8.183%	$43.2516	$43.25	$43.25	$43.30
Purchase #5	$66.61	10.419%	$73.5501	$73.55	$73.55	$73.60
Purchase #6	$115.47	6.784%	$123.3035	$123.30	$123.30	$123.30
Purchase #7	$157.55	7.569%	$169.475	$169.48	$169.50	$169.50
7 purchase totals =	$788.81		$854.5388	$854.54	$854.55	$854.60