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	$197.71	10.154%	$217.7855	$217.79	$217.80	$217.80
Purchase #2	$124.72	11.550%	$139.1252	$139.13	$139.15	$139.10
Purchase #3	$147.52	10.181%	$162.539	$162.54	$162.55	$162.50
Purchase #4	$182.67	12.201%	$204.9576	$204.96	$204.95	$205.00
Purchase #5	$164.87	12.415%	$185.3386	$185.34	$185.35	$185.30
Purchase #6	$6.97	9.205%	$7.6116	$7.61	$7.60	$7.60
Purchase #7	$154.60	3.586%	$160.144	$160.14	$160.15	$160.10
7 purchase totals =	$979.06		$1,077.5015	$1,077.51	$1,077.55	$1,077.40