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	$63.33	3.245%	$65.3851	$65.39	$65.40	$65.40
Purchase #2	$78.73	9.600%	$86.2881	$86.29	$86.30	$86.30
Purchase #3	$223.63	9.776%	$245.4921	$245.49	$245.50	$245.50
Purchase #4	$136.84	13.178%	$154.8728	$154.87	$154.85	$154.90
Purchase #5	$38.56	4.722%	$40.3808	$40.38	$40.40	$40.40
Purchase #6	$31.66	9.798%	$34.762	$34.76	$34.75	$34.80
Purchase #7	$156.33	5.827%	$165.4393	$165.44	$165.45	$165.40
7 purchase totals =	$729.08		$792.6202	$792.62	$792.65	$792.70