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	$152.59	3.789%	$158.3716	$158.37	$158.35	$158.40
Purchase #2	$155.96	12.582%	$175.5829	$175.58	$175.60	$175.60
Purchase #3	$92.54	13.344%	$104.8885	$104.89	$104.90	$104.90
Purchase #4	$11.33	7.754%	$12.2085	$12.21	$12.20	$12.20
Purchase #5	$103.86	7.470%	$111.6183	$111.62	$111.60	$111.60
Purchase #6	$174.30	11.356%	$194.0935	$194.09	$194.10	$194.10
Purchase #7	$232.62	11.753%	$259.9598	$259.96	$259.95	$260.00
7 purchase totals =	$923.20		$1,016.7231	$1,016.72	$1,016.70	$1,016.80