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	$131.36	8.735%	$142.8343	$142.83	$142.85	$142.80
Purchase #2	$152.26	10.408%	$168.1072	$168.11	$168.10	$168.10
Purchase #3	$168.25	10.556%	$186.0105	$186.01	$186.00	$186.00
Purchase #4	$68.92	3.624%	$71.4177	$71.42	$71.40	$71.40
Purchase #5	$188.59	13.176%	$213.4386	$213.44	$213.45	$213.40
Purchase #6	$145.44	6.652%	$155.1147	$155.11	$155.10	$155.10
Purchase #7	$141.46	9.639%	$155.0953	$155.10	$155.10	$155.10
7 purchase totals =	$996.28		$1,092.0183	$1,092.02	$1,092.00	$1,091.90