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	$218.99	4.789%	$229.4774	$229.48	$229.50	$229.50
Purchase #2	$118.95	10.627%	$131.5908	$131.59	$131.60	$131.60
Purchase #3	$246.73	7.122%	$264.3021	$264.30	$264.30	$264.30
Purchase #4	$118.57	6.797%	$126.6292	$126.63	$126.65	$126.60
Purchase #5	$150.80	8.682%	$163.8925	$163.89	$163.90	$163.90
Purchase #6	$103.45	6.140%	$109.8018	$109.80	$109.80	$109.80
Purchase #7	$51.91	3.284%	$53.6147	$53.61	$53.60	$53.60
7 purchase totals =	$1,009.40		$1,079.3085	$1,079.30	$1,079.35	$1,079.30