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	$168.69	8.350%	$182.7756	$182.78	$182.80	$182.80
Purchase #2	$82.84	4.674%	$86.7119	$86.71	$86.70	$86.70
Purchase #3	$88.77	8.727%	$96.517	$96.52	$96.50	$96.50
Purchase #4	$11.80	8.459%	$12.7982	$12.80	$12.80	$12.80
Purchase #5	$34.66	12.328%	$38.9329	$38.93	$38.95	$38.90
Purchase #6	$98.26	13.860%	$111.8788	$111.88	$111.90	$111.90
Purchase #7	$201.36	10.166%	$221.8303	$221.83	$221.85	$221.80
7 purchase totals =	$686.38		$751.4447	$751.45	$751.50	$751.40