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	$192.79	9.225%	$210.5749	$210.57	$210.55	$210.60
Purchase #2	$73.49	9.302%	$80.326	$80.33	$80.35	$80.30
Purchase #3	$54.34	5.709%	$57.4423	$57.44	$57.45	$57.40
Purchase #4	$22.61	10.694%	$25.0279	$25.03	$25.05	$25.00
Purchase #5	$183.30	5.128%	$192.6996	$192.70	$192.70	$192.70
Purchase #6	$35.47	13.771%	$40.3546	$40.35	$40.35	$40.40
Purchase #7	$54.69	12.111%	$61.3135	$61.31	$61.30	$61.30
7 purchase totals =	$616.69		$667.7388	$667.73	$667.75	$667.70