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	$96.95	7.532%	$104.2523	$104.25	$104.25	$104.30
Purchase #2	$131.32	5.456%	$138.4848	$138.48	$138.50	$138.50
Purchase #3	$124.72	13.328%	$141.3427	$141.34	$141.35	$141.30
Purchase #4	$211.39	10.788%	$234.1948	$234.19	$234.20	$234.20
Purchase #5	$167.46	13.823%	$190.608	$190.61	$190.60	$190.60
Purchase #6	$62.32	8.812%	$67.8116	$67.81	$67.80	$67.80
Purchase #7	$194.41	11.646%	$217.051	$217.05	$217.05	$217.10
7 purchase totals =	$988.57		$1,093.7452	$1,093.73	$1,093.75	$1,093.80