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	$62.28	12.855%	$70.2861	$70.29	$70.30	$70.30
Purchase #2	$77.61	7.309%	$83.2825	$83.28	$83.30	$83.30
Purchase #3	$78.35	7.768%	$84.4362	$84.44	$84.45	$84.40
Purchase #4	$185.70	7.500%	$199.6275	$199.63	$199.65	$199.60
Purchase #5	$250.89	10.216%	$276.5209	$276.52	$276.50	$276.50
Purchase #6	$174.56	5.857%	$184.784	$184.78	$184.80	$184.80
Purchase #7	$242.29	5.610%	$255.8825	$255.88	$255.90	$255.90
7 purchase totals =	$1,071.68		$1,154.8197	$1,154.82	$1,154.90	$1,154.80