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	$10.84	6.572%	$11.5524	$11.55	$11.55	$11.60
Purchase #2	$90.33	6.697%	$96.3794	$96.38	$96.40	$96.40
Purchase #3	$138.93	3.197%	$143.3716	$143.37	$143.35	$143.40
Purchase #4	$166.76	12.854%	$188.1953	$188.20	$188.20	$188.20
Purchase #5	$149.27	3.603%	$154.6482	$154.65	$154.65	$154.60
Purchase #6	$130.53	6.705%	$139.282	$139.28	$139.30	$139.30
Purchase #7	$50.83	4.328%	$53.0299	$53.03	$53.05	$53.00
7 purchase totals =	$737.49		$786.4588	$786.46	$786.50	$786.50