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	$165.80	12.814%	$187.0456	$187.05	$187.05	$187.00
Purchase #2	$44.44	5.336%	$46.8113	$46.81	$46.80	$46.80
Purchase #3	$29.30	12.516%	$32.9672	$32.97	$32.95	$33.00
Purchase #4	$71.44	9.190%	$78.0053	$78.01	$78.00	$78.00
Purchase #5	$196.46	7.722%	$211.6306	$211.63	$211.65	$211.60
Purchase #6	$81.91	10.828%	$90.7792	$90.78	$90.80	$90.80
Purchase #7	$89.31	6.790%	$95.3741	$95.37	$95.35	$95.40
7 purchase totals =	$678.66		$742.6133	$742.62	$742.60	$742.60