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	$194.53	9.392%	$212.8003	$212.80	$212.80	$212.80
Purchase #2	$151.69	12.766%	$171.0547	$171.05	$171.05	$171.10
Purchase #3	$171.62	7.544%	$184.567	$184.57	$184.55	$184.60
Purchase #4	$129.81	8.541%	$140.8971	$140.90	$140.90	$140.90
Purchase #5	$127.75	3.234%	$131.8814	$131.88	$131.90	$131.90
Purchase #6	$90.56	5.361%	$95.4149	$95.41	$95.40	$95.40
Purchase #7	$173.25	9.815%	$190.2545	$190.25	$190.25	$190.30
7 purchase totals =	$1,039.21		$1,126.8699	$1,126.86	$1,126.85	$1,127.00