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	$221.72	6.338%	$235.7726	$235.77	$235.75	$235.80
Purchase #2	$54.70	9.326%	$59.8013	$59.80	$59.80	$59.80
Purchase #3	$68.45	9.446%	$74.9158	$74.92	$74.90	$74.90
Purchase #4	$75.40	6.593%	$80.3711	$80.37	$80.35	$80.40
Purchase #5	$246.57	3.266%	$254.623	$254.62	$254.60	$254.60
Purchase #6	$100.69	10.683%	$111.4467	$111.45	$111.45	$111.40
Purchase #7	$84.31	6.299%	$89.6207	$89.62	$89.60	$89.60
7 purchase totals =	$851.84		$906.5512	$906.55	$906.45	$906.50