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	$209.52	6.228%	$222.5689	$222.57	$222.55	$222.60
Purchase #2	$86.70	4.738%	$90.8078	$90.81	$90.80	$90.80
Purchase #3	$115.58	11.729%	$129.1364	$129.14	$129.15	$129.10
Purchase #4	$52.47	10.304%	$57.8765	$57.88	$57.90	$57.90
Purchase #5	$31.49	3.357%	$32.5471	$32.55	$32.55	$32.50
Purchase #6	$149.43	12.192%	$167.6485	$167.65	$167.65	$167.60
Purchase #7	$82.56	13.646%	$93.8261	$93.83	$93.85	$93.80
7 purchase totals =	$727.75		$794.4113	$794.43	$794.45	$794.30