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	$123.25	6.377%	$131.1097	$131.11	$131.10	$131.10
Purchase #2	$31.83	13.854%	$36.2397	$36.24	$36.25	$36.20
Purchase #3	$160.98	4.193%	$167.7299	$167.73	$167.75	$167.70
Purchase #4	$134.60	5.342%	$141.7903	$141.79	$141.80	$141.80
Purchase #5	$137.30	13.679%	$156.0813	$156.08	$156.10	$156.10
Purchase #6	$77.84	5.637%	$82.2278	$82.23	$82.25	$82.20
Purchase #7	$202.61	7.802%	$218.4176	$218.42	$218.40	$218.40
7 purchase totals =	$868.41		$933.5963	$933.60	$933.65	$933.50