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	$148.69	12.469%	$167.2302	$167.23	$167.25	$167.20
Purchase #2	$108.37	13.822%	$123.3489	$123.35	$123.35	$123.30
Purchase #3	$112.76	9.786%	$123.7947	$123.79	$123.80	$123.80
Purchase #4	$71.89	9.428%	$78.6678	$78.67	$78.65	$78.70
Purchase #5	$43.46	5.679%	$45.9281	$45.93	$45.95	$45.90
Purchase #6	$225.63	7.302%	$242.1055	$242.11	$242.10	$242.10
Purchase #7	$158.76	8.183%	$171.7513	$171.75	$171.75	$171.80
7 purchase totals =	$869.56		$952.8265	$952.83	$952.85	$952.80