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	$187.83	7.124%	$201.211	$201.21	$201.20	$201.20
Purchase #2	$99.54	9.812%	$109.3069	$109.31	$109.30	$109.30
Purchase #3	$137.59	5.383%	$144.9965	$145.00	$145.00	$145.00
Purchase #4	$105.60	8.535%	$114.613	$114.61	$114.60	$114.60
Purchase #5	$177.53	4.711%	$185.8934	$185.89	$185.90	$185.90
Purchase #6	$204.81	11.633%	$228.6355	$228.64	$228.65	$228.60
Purchase #7	$59.69	10.105%	$65.7217	$65.72	$65.70	$65.70
7 purchase totals =	$972.59		$1,050.3780	$1,050.38	$1,050.35	$1,050.30