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	$42.87	7.794%	$46.2113	$46.21	$46.20	$46.20
Purchase #2	$118.74	3.674%	$123.1025	$123.10	$123.10	$123.10
Purchase #3	$63.34	5.805%	$67.0169	$67.02	$67.00	$67.00
Purchase #4	$80.90	10.339%	$89.2643	$89.26	$89.25	$89.30
Purchase #5	$161.62	3.498%	$167.2735	$167.27	$167.25	$167.30
Purchase #6	$30.45	10.195%	$33.5544	$33.55	$33.55	$33.60
Purchase #7	$210.97	9.533%	$231.0818	$231.08	$231.10	$231.10
7 purchase totals =	$708.89		$757.5047	$757.49	$757.45	$757.60