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	$215.55	3.549%	$223.1999	$223.20	$223.20	$223.20
Purchase #2	$91.72	3.414%	$94.8513	$94.85	$94.85	$94.90
Purchase #3	$232.39	7.535%	$249.9006	$249.90	$249.90	$249.90
Purchase #4	$238.62	4.393%	$249.1026	$249.10	$249.10	$249.10
Purchase #5	$70.59	10.574%	$78.0542	$78.05	$78.05	$78.10
Purchase #6	$50.57	3.284%	$52.2307	$52.23	$52.25	$52.20
Purchase #7	$211.66	5.633%	$223.5828	$223.58	$223.60	$223.60
7 purchase totals =	$1,111.10		$1,170.9221	$1,170.91	$1,170.95	$1,171.00