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	$175.44	3.161%	$180.9857	$180.99	$181.00	$181.00
Purchase #2	$162.55	5.746%	$171.8901	$171.89	$171.90	$171.90
Purchase #3	$68.57	13.820%	$78.0464	$78.05	$78.05	$78.00
Purchase #4	$90.60	13.587%	$102.9098	$102.91	$102.90	$102.90
Purchase #5	$134.32	6.360%	$142.8628	$142.86	$142.85	$142.90
Purchase #6	$195.38	11.251%	$217.3622	$217.36	$217.35	$217.40
Purchase #7	$177.78	3.708%	$184.3721	$184.37	$184.35	$184.40
7 purchase totals =	$1,004.64		$1,078.4291	$1,078.43	$1,078.40	$1,078.50