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	$216.51	12.432%	$243.4265	$243.43	$243.45	$243.40
Purchase #2	$211.35	4.685%	$221.2517	$221.25	$221.25	$221.30
Purchase #3	$137.77	5.429%	$145.2495	$145.25	$145.25	$145.20
Purchase #4	$249.83	8.598%	$271.3104	$271.31	$271.30	$271.30
Purchase #5	$82.76	7.689%	$89.1234	$89.12	$89.10	$89.10
Purchase #6	$8.25	4.578%	$8.6277	$8.63	$8.65	$8.60
Purchase #7	$198.31	9.207%	$216.5684	$216.57	$216.55	$216.60
7 purchase totals =	$1,104.78		$1,195.5576	$1,195.56	$1,195.55	$1,195.50