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	$62.32	13.692%	$70.8529	$70.85	$70.85	$70.90
Purchase #2	$56.65	7.501%	$60.8993	$60.90	$60.90	$60.90
Purchase #3	$204.45	3.117%	$210.8227	$210.82	$210.80	$210.80
Purchase #4	$84.79	7.242%	$90.9305	$90.93	$90.95	$90.90
Purchase #5	$245.78	7.136%	$263.3189	$263.32	$263.30	$263.30
Purchase #6	$217.39	3.630%	$225.2813	$225.28	$225.30	$225.30
Purchase #7	$213.77	13.566%	$242.77	$242.77	$242.75	$242.80
7 purchase totals =	$1,085.15		$1,164.8756	$1,164.87	$1,164.85	$1,164.90