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	$59.88	8.510%	$64.9758	$64.98	$65.00	$65.00
Purchase #2	$164.29	13.557%	$186.5628	$186.56	$186.55	$186.60
Purchase #3	$130.83	12.623%	$147.3447	$147.34	$147.35	$147.30
Purchase #4	$192.97	5.373%	$203.3383	$203.34	$203.35	$203.30
Purchase #5	$40.42	4.611%	$42.2838	$42.28	$42.30	$42.30
Purchase #6	$236.25	6.198%	$250.8928	$250.89	$250.90	$250.90
Purchase #7	$208.55	6.574%	$222.2601	$222.26	$222.25	$222.30
7 purchase totals =	$1,033.19		$1,117.6583	$1,117.65	$1,117.70	$1,117.70