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	$178.97	12.498%	$201.3377	$201.34	$201.35	$201.30
Purchase #2	$78.98	5.107%	$83.0135	$83.01	$83.00	$83.00
Purchase #3	$156.63	3.682%	$162.3971	$162.40	$162.40	$162.40
Purchase #4	$138.32	9.786%	$151.856	$151.86	$151.85	$151.90
Purchase #5	$79.39	10.191%	$87.4806	$87.48	$87.50	$87.50
Purchase #6	$240.46	6.615%	$256.3664	$256.37	$256.35	$256.40
Purchase #7	$147.35	3.710%	$152.8167	$152.82	$152.80	$152.80
7 purchase totals =	$1,020.10		$1,095.2680	$1,095.28	$1,095.25	$1,095.30