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	$214.31	8.772%	$233.1093	$233.11	$233.10	$233.10
Purchase #2	$81.86	8.856%	$89.1095	$89.11	$89.10	$89.10
Purchase #3	$231.94	10.514%	$256.3262	$256.33	$256.35	$256.30
Purchase #4	$192.40	8.614%	$208.9733	$208.97	$208.95	$209.00
Purchase #5	$94.38	13.864%	$107.4648	$107.46	$107.45	$107.50
Purchase #6	$213.61	11.587%	$238.361	$238.36	$238.35	$238.40
Purchase #7	$30.96	9.148%	$33.7922	$33.79	$33.80	$33.80
7 purchase totals =	$1,059.46		$1,167.1363	$1,167.13	$1,167.10	$1,167.20