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	$150.92	12.489%	$169.7684	$169.77	$169.75	$169.80
Purchase #2	$144.83	8.573%	$157.2463	$157.25	$157.25	$157.20
Purchase #3	$68.99	13.607%	$78.3775	$78.38	$78.40	$78.40
Purchase #4	$139.31	6.423%	$148.2579	$148.26	$148.25	$148.30
Purchase #5	$52.47	10.259%	$57.8529	$57.85	$57.85	$57.90
Purchase #6	$64.52	13.293%	$73.0966	$73.10	$73.10	$73.10
Purchase #7	$18.39	13.398%	$20.8539	$20.85	$20.85	$20.90
7 purchase totals =	$639.43		$705.4535	$705.46	$705.45	$705.60