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	$222.39	13.190%	$251.7232	$251.72	$251.70	$251.70
Purchase #2	$222.57	4.260%	$232.0515	$232.05	$232.05	$232.10
Purchase #3	$73.39	13.213%	$83.087	$83.09	$83.10	$83.10
Purchase #4	$202.60	12.762%	$228.4558	$228.46	$228.45	$228.50
Purchase #5	$96.37	13.726%	$109.5977	$109.60	$109.60	$109.60
Purchase #6	$150.78	11.843%	$168.6369	$168.64	$168.65	$168.60
Purchase #7	$126.96	3.785%	$131.7654	$131.77	$131.75	$131.80
7 purchase totals =	$1,095.06		$1,205.3175	$1,205.33	$1,205.30	$1,205.40