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	$54.79	11.419%	$61.0465	$61.05	$61.05	$61.00
Purchase #2	$61.51	7.667%	$66.226	$66.23	$66.25	$66.20
Purchase #3	$160.70	4.116%	$167.3144	$167.31	$167.30	$167.30
Purchase #4	$177.57	7.427%	$190.7581	$190.76	$190.75	$190.80
Purchase #5	$131.75	6.658%	$140.5219	$140.52	$140.50	$140.50
Purchase #6	$231.97	6.292%	$246.5656	$246.57	$246.55	$246.60
Purchase #7	$126.50	11.390%	$140.9084	$140.91	$140.90	$140.90
7 purchase totals =	$944.79		$1,013.3409	$1,013.35	$1,013.30	$1,013.30