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	$116.34	12.630%	$131.0337	$131.03	$131.05	$131.00
Purchase #2	$136.87	11.236%	$152.2487	$152.25	$152.25	$152.20
Purchase #3	$10.27	10.162%	$11.3136	$11.31	$11.30	$11.30
Purchase #4	$211.82	13.108%	$239.5854	$239.59	$239.60	$239.60
Purchase #5	$178.99	5.656%	$189.1137	$189.11	$189.10	$189.10
Purchase #6	$131.99	7.134%	$141.4062	$141.41	$141.40	$141.40
Purchase #7	$69.76	3.623%	$72.2874	$72.29	$72.30	$72.30
7 purchase totals =	$856.04		$936.9887	$936.99	$937.00	$936.90