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	$225.37	10.651%	$249.3742	$249.37	$249.35	$249.40
Purchase #2	$132.98	3.498%	$137.6316	$137.63	$137.65	$137.60
Purchase #3	$103.76	5.495%	$109.4616	$109.46	$109.45	$109.50
Purchase #4	$132.87	5.461%	$140.126	$140.13	$140.15	$140.10
Purchase #5	$232.74	4.244%	$242.6175	$242.62	$242.60	$242.60
Purchase #6	$75.33	12.789%	$84.964	$84.96	$84.95	$85.00
Purchase #7	$54.80	9.294%	$59.8931	$59.89	$59.90	$59.90
7 purchase totals =	$957.85		$1,024.0680	$1,024.06	$1,024.05	$1,024.10