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	$21.71	4.835%	$22.7597	$22.76	$22.75	$22.80
Purchase #2	$250.58	4.843%	$262.7156	$262.72	$262.70	$262.70
Purchase #3	$52.47	12.698%	$59.1326	$59.13	$59.15	$59.10
Purchase #4	$87.82	11.165%	$97.6251	$97.63	$97.65	$97.60
Purchase #5	$179.27	8.798%	$195.0422	$195.04	$195.05	$195.00
Purchase #6	$43.60	3.852%	$45.2795	$45.28	$45.30	$45.30
Purchase #7	$90.50	8.678%	$98.3536	$98.35	$98.35	$98.40
7 purchase totals =	$725.95		$780.9083	$780.91	$780.95	$780.90