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	$77.77	12.335%	$87.3629	$87.36	$87.35	$87.40
Purchase #2	$19.88	4.170%	$20.709	$20.71	$20.70	$20.70
Purchase #3	$122.44	7.692%	$131.8581	$131.86	$131.85	$131.90
Purchase #4	$52.50	4.323%	$54.7696	$54.77	$54.75	$54.80
Purchase #5	$223.28	13.498%	$253.4183	$253.42	$253.40	$253.40
Purchase #6	$57.69	9.223%	$63.0107	$63.01	$63.00	$63.00
Purchase #7	$60.37	9.743%	$66.2518	$66.25	$66.25	$66.30
7 purchase totals =	$613.93		$677.3804	$677.38	$677.30	$677.50