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	$209.53	4.126%	$218.1752	$218.18	$218.20	$218.20
Purchase #2	$53.98	3.849%	$56.0577	$56.06	$56.05	$56.10
Purchase #3	$194.32	6.289%	$206.5408	$206.54	$206.55	$206.50
Purchase #4	$31.95	3.647%	$33.1152	$33.12	$33.10	$33.10
Purchase #5	$200.88	3.590%	$208.0916	$208.09	$208.10	$208.10
Purchase #6	$235.63	8.357%	$255.3216	$255.32	$255.30	$255.30
Purchase #7	$92.95	13.310%	$105.3216	$105.32	$105.30	$105.30
7 purchase totals =	$1,019.24		$1,082.6237	$1,082.63	$1,082.60	$1,082.60