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	$122.56	4.308%	$127.8399	$127.84	$127.85	$127.80
Purchase #2	$108.84	4.348%	$113.5724	$113.57	$113.55	$113.60
Purchase #3	$180.82	4.809%	$189.5156	$189.52	$189.50	$189.50
Purchase #4	$23.33	12.366%	$26.215	$26.22	$26.20	$26.20
Purchase #5	$133.49	6.615%	$142.3204	$142.32	$142.30	$142.30
Purchase #6	$21.89	8.208%	$23.6867	$23.69	$23.70	$23.70
Purchase #7	$53.39	11.369%	$59.4599	$59.46	$59.45	$59.50
7 purchase totals =	$644.32		$682.6099	$682.62	$682.55	$682.60