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	$228.86	11.533%	$255.2544	$255.25	$255.25	$255.30
Purchase #2	$198.40	7.817%	$213.9089	$213.91	$213.90	$213.90
Purchase #3	$174.89	13.654%	$198.7695	$198.77	$198.75	$198.80
Purchase #4	$208.70	7.297%	$223.9288	$223.93	$223.95	$223.90
Purchase #5	$201.60	13.352%	$228.5176	$228.52	$228.50	$228.50
Purchase #6	$183.78	11.426%	$204.7787	$204.78	$204.80	$204.80
Purchase #7	$52.57	3.533%	$54.4273	$54.43	$54.45	$54.40
7 purchase totals =	$1,248.80		$1,379.5852	$1,379.59	$1,379.60	$1,379.60