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	$200.71	4.301%	$209.3425	$209.34	$209.35	$209.30
Purchase #2	$57.52	4.140%	$59.9013	$59.90	$59.90	$59.90
Purchase #3	$195.83	9.466%	$214.3673	$214.37	$214.35	$214.40
Purchase #4	$111.91	3.114%	$115.3949	$115.39	$115.40	$115.40
Purchase #5	$10.38	12.286%	$11.6553	$11.66	$11.65	$11.70
Purchase #6	$169.68	12.697%	$191.2243	$191.22	$191.20	$191.20
Purchase #7	$5.78	12.495%	$6.5022	$6.50	$6.50	$6.50
7 purchase totals =	$751.81		$808.3878	$808.38	$808.35	$808.40