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	$172.97	11.236%	$192.4049	$192.40	$192.40	$192.40
Purchase #2	$176.35	10.506%	$194.8773	$194.88	$194.90	$194.90
Purchase #3	$188.89	4.222%	$196.8649	$196.86	$196.85	$196.90
Purchase #4	$77.56	7.155%	$83.1094	$83.11	$83.10	$83.10
Purchase #5	$184.45	11.866%	$206.3368	$206.34	$206.35	$206.30
Purchase #6	$151.32	13.366%	$171.5454	$171.55	$171.55	$171.50
Purchase #7	$239.54	8.523%	$259.956	$259.96	$259.95	$260.00
7 purchase totals =	$1,191.08		$1,305.0947	$1,305.10	$1,305.10	$1,305.10