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	$223.73	10.158%	$246.4565	$246.46	$246.45	$246.50
Purchase #2	$68.33	8.141%	$73.8927	$73.89	$73.90	$73.90
Purchase #3	$28.90	7.261%	$30.9984	$31.00	$31.00	$31.00
Purchase #4	$162.27	5.400%	$171.0326	$171.03	$171.05	$171.00
Purchase #5	$147.63	13.483%	$167.535	$167.54	$167.55	$167.50
Purchase #6	$65.66	9.385%	$71.8222	$71.82	$71.80	$71.80
Purchase #7	$5.89	7.678%	$6.3422	$6.34	$6.35	$6.30
7 purchase totals =	$702.41		$768.0796	$768.08	$768.10	$768.00