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	$177.38	13.271%	$200.9201	$200.92	$200.90	$200.90
Purchase #2	$79.35	5.223%	$83.4945	$83.49	$83.50	$83.50
Purchase #3	$250.37	5.637%	$264.4834	$264.48	$264.50	$264.50
Purchase #4	$249.98	11.112%	$277.7578	$277.76	$277.75	$277.80
Purchase #5	$178.77	6.571%	$190.517	$190.52	$190.50	$190.50
Purchase #6	$44.45	9.649%	$48.739	$48.74	$48.75	$48.70
Purchase #7	$70.39	10.343%	$77.6704	$77.67	$77.65	$77.70
7 purchase totals =	$1,050.69		$1,143.5822	$1,143.58	$1,143.55	$1,143.60