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	$168.39	7.571%	$181.1388	$181.14	$181.15	$181.10
Purchase #2	$218.86	8.725%	$237.9555	$237.96	$237.95	$238.00
Purchase #3	$185.68	7.792%	$200.1482	$200.15	$200.15	$200.10
Purchase #4	$196.34	6.757%	$209.6067	$209.61	$209.60	$209.60
Purchase #5	$154.69	13.825%	$176.0759	$176.08	$176.10	$176.10
Purchase #6	$99.73	6.169%	$105.8823	$105.88	$105.90	$105.90
Purchase #7	$70.41	11.349%	$78.4008	$78.40	$78.40	$78.40
7 purchase totals =	$1,094.10		$1,189.2082	$1,189.22	$1,189.25	$1,189.20