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	$67.75	7.838%	$73.0602	$73.06	$73.05	$73.10
Purchase #2	$201.42	13.288%	$228.1847	$228.18	$228.20	$228.20
Purchase #3	$219.58	4.385%	$229.2086	$229.21	$229.20	$229.20
Purchase #4	$98.71	12.535%	$111.0833	$111.08	$111.10	$111.10
Purchase #5	$78.88	9.861%	$86.6584	$86.66	$86.65	$86.70
Purchase #6	$65.43	3.252%	$67.5578	$67.56	$67.55	$67.60
Purchase #7	$128.31	13.482%	$145.6088	$145.61	$145.60	$145.60
7 purchase totals =	$860.08		$941.3618	$941.36	$941.35	$941.50