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	$126.68	12.178%	$142.1071	$142.11	$142.10	$142.10
Purchase #2	$107.85	8.790%	$117.33	$117.33	$117.35	$117.30
Purchase #3	$98.27	13.191%	$111.2328	$111.23	$111.25	$111.20
Purchase #4	$53.88	10.791%	$59.6942	$59.69	$59.70	$59.70
Purchase #5	$182.43	4.318%	$190.3073	$190.31	$190.30	$190.30
Purchase #6	$87.25	4.466%	$91.1466	$91.15	$91.15	$91.10
Purchase #7	$164.34	4.522%	$171.7715	$171.77	$171.75	$171.80
7 purchase totals =	$820.70		$883.5895	$883.59	$883.60	$883.50