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	$153.75	13.443%	$174.4186	$174.42	$174.40	$174.40
Purchase #2	$250.41	9.181%	$273.4001	$273.40	$273.40	$273.40
Purchase #3	$164.51	10.796%	$182.2705	$182.27	$182.25	$182.30
Purchase #4	$178.88	3.500%	$185.1408	$185.14	$185.15	$185.10
Purchase #5	$56.62	8.282%	$61.3093	$61.31	$61.30	$61.30
Purchase #6	$18.54	4.130%	$19.3057	$19.31	$19.30	$19.30
Purchase #7	$135.54	5.162%	$142.5366	$142.54	$142.55	$142.50
7 purchase totals =	$958.25		$1,038.3816	$1,038.39	$1,038.35	$1,038.30