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	$200.57	7.203%	$215.0171	$215.02	$215.00	$215.00
Purchase #2	$228.54	9.103%	$249.344	$249.34	$249.35	$249.30
Purchase #3	$142.88	9.819%	$156.9094	$156.91	$156.90	$156.90
Purchase #4	$236.71	10.285%	$261.0556	$261.06	$261.05	$261.10
Purchase #5	$72.93	6.787%	$77.8798	$77.88	$77.90	$77.90
Purchase #6	$164.28	7.545%	$176.6749	$176.67	$176.65	$176.70
Purchase #7	$64.52	12.304%	$72.4585	$72.46	$72.45	$72.50
7 purchase totals =	$1,110.43		$1,209.3393	$1,209.34	$1,209.30	$1,209.40