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	$41.59	13.807%	$47.3323	$47.33	$47.35	$47.30
Purchase #2	$52.58	4.220%	$54.7989	$54.80	$54.80	$54.80
Purchase #3	$100.26	8.773%	$109.0558	$109.06	$109.05	$109.10
Purchase #4	$65.33	3.583%	$67.6708	$67.67	$67.65	$67.70
Purchase #5	$48.75	7.211%	$52.2654	$52.27	$52.25	$52.30
Purchase #6	$143.42	11.600%	$160.0567	$160.06	$160.05	$160.10
Purchase #7	$66.32	4.513%	$69.313	$69.31	$69.30	$69.30
7 purchase totals =	$518.25		$560.4929	$560.50	$560.45	$560.60