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	$160.97	11.591%	$179.628	$179.63	$179.65	$179.60
Purchase #2	$221.67	10.118%	$244.0986	$244.10	$244.10	$244.10
Purchase #3	$117.61	9.477%	$128.7559	$128.76	$128.75	$128.80
Purchase #4	$165.62	13.603%	$188.1493	$188.15	$188.15	$188.10
Purchase #5	$177.38	7.272%	$190.2791	$190.28	$190.30	$190.30
Purchase #6	$137.80	13.217%	$156.013	$156.01	$156.00	$156.00
Purchase #7	$112.40	10.192%	$123.8558	$123.86	$123.85	$123.90
7 purchase totals =	$1,093.45		$1,210.7797	$1,210.79	$1,210.80	$1,210.80