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	$118.62	8.543%	$128.7537	$128.75	$128.75	$128.80
Purchase #2	$248.25	4.172%	$258.607	$258.61	$258.60	$258.60
Purchase #3	$142.95	10.373%	$157.7782	$157.78	$157.80	$157.80
Purchase #4	$55.70	6.752%	$59.4609	$59.46	$59.45	$59.50
Purchase #5	$197.69	9.133%	$215.745	$215.75	$215.75	$215.70
Purchase #6	$51.42	6.113%	$54.5633	$54.56	$54.55	$54.60
Purchase #7	$30.97	8.333%	$33.5507	$33.55	$33.55	$33.60
7 purchase totals =	$845.60		$908.4588	$908.46	$908.45	$908.60