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	$222.42	7.156%	$238.3364	$238.34	$238.35	$238.30
Purchase #2	$84.99	5.225%	$89.4307	$89.43	$89.45	$89.40
Purchase #3	$150.32	13.778%	$171.0311	$171.03	$171.05	$171.00
Purchase #4	$31.29	7.245%	$33.557	$33.56	$33.55	$33.60
Purchase #5	$96.51	12.743%	$108.8083	$108.81	$108.80	$108.80
Purchase #6	$154.86	8.698%	$168.3297	$168.33	$168.35	$168.30
Purchase #7	$171.74	13.336%	$194.6432	$194.64	$194.65	$194.60
7 purchase totals =	$912.13		$1,004.1364	$1,004.14	$1,004.20	$1,004.00