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	$57.37	8.594%	$62.3004	$62.30	$62.30	$62.30
Purchase #2	$153.61	13.444%	$174.2613	$174.26	$174.25	$174.30
Purchase #3	$108.98	3.158%	$112.4216	$112.42	$112.40	$112.40
Purchase #4	$109.54	10.387%	$120.9179	$120.92	$120.90	$120.90
Purchase #5	$39.63	7.739%	$42.697	$42.70	$42.70	$42.70
Purchase #6	$100.66	5.268%	$105.9628	$105.96	$105.95	$106.00
Purchase #7	$133.39	6.350%	$141.8603	$141.86	$141.85	$141.90
7 purchase totals =	$703.18		$760.4213	$760.42	$760.35	$760.50