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	$50.51	4.855%	$52.9623	$52.96	$52.95	$53.00
Purchase #2	$229.51	5.358%	$241.8071	$241.81	$241.80	$241.80
Purchase #3	$53.87	10.579%	$59.5689	$59.57	$59.55	$59.60
Purchase #4	$114.57	4.539%	$119.7703	$119.77	$119.75	$119.80
Purchase #5	$142.43	6.188%	$151.2436	$151.24	$151.25	$151.20
Purchase #6	$61.97	13.494%	$70.3322	$70.33	$70.35	$70.30
Purchase #7	$205.27	8.269%	$222.2438	$222.24	$222.25	$222.20
7 purchase totals =	$858.13		$917.9282	$917.92	$917.90	$917.90