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	$168.98	10.684%	$187.0338	$187.03	$187.05	$187.00
Purchase #2	$114.93	13.872%	$130.8731	$130.87	$130.85	$130.90
Purchase #3	$83.41	7.430%	$89.6074	$89.61	$89.60	$89.60
Purchase #4	$136.67	4.137%	$142.324	$142.32	$142.30	$142.30
Purchase #5	$101.39	9.873%	$111.4002	$111.40	$111.40	$111.40
Purchase #6	$199.37	3.750%	$206.8464	$206.85	$206.85	$206.80
Purchase #7	$206.96	6.840%	$221.1161	$221.12	$221.10	$221.10
7 purchase totals =	$1,011.71		$1,089.2010	$1,089.20	$1,089.15	$1,089.10