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	$103.45	7.546%	$111.2563	$111.26	$111.25	$111.30
Purchase #2	$54.33	5.776%	$57.4681	$57.47	$57.45	$57.50
Purchase #3	$144.96	4.702%	$151.776	$151.78	$151.80	$151.80
Purchase #4	$58.56	10.674%	$64.8107	$64.81	$64.80	$64.80
Purchase #5	$45.83	6.550%	$48.8319	$48.83	$48.85	$48.80
Purchase #6	$171.83	5.291%	$180.9215	$180.92	$180.90	$180.90
Purchase #7	$36.37	6.848%	$38.8606	$38.86	$38.85	$38.90
7 purchase totals =	$615.33		$653.9251	$653.93	$653.90	$654.00