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	$148.67	12.426%	$167.1437	$167.14	$167.15	$167.10
Purchase #2	$134.52	6.686%	$143.514	$143.51	$143.50	$143.50
Purchase #3	$151.31	6.417%	$161.0196	$161.02	$161.00	$161.00
Purchase #4	$174.61	10.827%	$193.515	$193.52	$193.50	$193.50
Purchase #5	$86.42	9.383%	$94.5288	$94.53	$94.55	$94.50
Purchase #6	$150.50	12.119%	$168.7391	$168.74	$168.75	$168.70
Purchase #7	$244.32	7.476%	$262.5854	$262.59	$262.60	$262.60
7 purchase totals =	$1,090.35		$1,191.0456	$1,191.05	$1,191.05	$1,190.90