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	$102.64	10.360%	$113.2735	$113.27	$113.25	$113.30
Purchase #2	$137.33	11.549%	$153.1902	$153.19	$153.20	$153.20
Purchase #3	$152.45	10.104%	$167.8535	$167.85	$167.85	$167.90
Purchase #4	$145.62	11.259%	$162.0154	$162.02	$162.00	$162.00
Purchase #5	$47.94	10.586%	$53.0149	$53.01	$53.00	$53.00
Purchase #6	$80.39	13.705%	$91.4074	$91.41	$91.40	$91.40
Purchase #7	$148.86	12.520%	$167.4973	$167.50	$167.50	$167.50
7 purchase totals =	$815.23		$908.2522	$908.25	$908.20	$908.30