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	$43.32	7.520%	$46.5777	$46.58	$46.60	$46.60
Purchase #2	$230.37	5.208%	$242.3677	$242.37	$242.35	$242.40
Purchase #3	$81.91	4.279%	$85.4149	$85.41	$85.40	$85.40
Purchase #4	$59.61	12.599%	$67.1203	$67.12	$67.10	$67.10
Purchase #5	$30.32	3.316%	$31.3254	$31.33	$31.35	$31.30
Purchase #6	$74.94	9.431%	$82.0076	$82.01	$82.00	$82.00
Purchase #7	$102.78	4.235%	$107.1327	$107.13	$107.15	$107.10
7 purchase totals =	$623.25		$661.9463	$661.95	$661.95	$661.90