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	$54.39	9.195%	$59.3912	$59.39	$59.40	$59.40
Purchase #2	$129.91	3.227%	$134.1022	$134.10	$134.10	$134.10
Purchase #3	$52.88	11.714%	$59.0744	$59.07	$59.05	$59.10
Purchase #4	$62.43	9.663%	$68.4626	$68.46	$68.45	$68.50
Purchase #5	$67.88	8.653%	$73.7537	$73.75	$73.75	$73.80
Purchase #6	$91.78	3.104%	$94.6289	$94.63	$94.65	$94.60
Purchase #7	$183.35	3.412%	$189.6059	$189.61	$189.60	$189.60
7 purchase totals =	$642.62		$679.0189	$679.01	$679.00	$679.10