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	$173.43	12.792%	$195.6152	$195.62	$195.60	$195.60
Purchase #2	$89.27	13.609%	$101.4188	$101.42	$101.40	$101.40
Purchase #3	$81.31	10.355%	$89.7297	$89.73	$89.75	$89.70
Purchase #4	$228.56	12.393%	$256.8854	$256.89	$256.90	$256.90
Purchase #5	$102.84	10.866%	$114.0146	$114.01	$114.00	$114.00
Purchase #6	$191.46	13.348%	$217.0161	$217.02	$217.00	$217.00
Purchase #7	$143.25	12.290%	$160.8554	$160.86	$160.85	$160.90
7 purchase totals =	$1,010.12		$1,135.5352	$1,135.55	$1,135.50	$1,135.50