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	$60.66	3.633%	$62.8638	$62.86	$62.85	$62.90
Purchase #2	$209.38	12.161%	$234.8427	$234.84	$234.85	$234.80
Purchase #3	$212.33	5.311%	$223.6068	$223.61	$223.60	$223.60
Purchase #4	$143.97	10.555%	$159.166	$159.17	$159.15	$159.20
Purchase #5	$49.59	10.530%	$54.8118	$54.81	$54.80	$54.80
Purchase #6	$176.48	5.326%	$185.8793	$185.88	$185.90	$185.90
Purchase #7	$19.29	6.194%	$20.4848	$20.48	$20.50	$20.50
7 purchase totals =	$871.70		$941.6552	$941.65	$941.65	$941.70