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	$208.48	13.613%	$236.8604	$236.86	$236.85	$236.90
Purchase #2	$186.55	5.495%	$196.8009	$196.80	$196.80	$196.80
Purchase #3	$219.91	10.555%	$243.1215	$243.12	$243.10	$243.10
Purchase #4	$88.71	12.352%	$99.6675	$99.67	$99.65	$99.70
Purchase #5	$104.77	6.520%	$111.601	$111.60	$111.60	$111.60
Purchase #6	$137.74	9.376%	$150.6545	$150.65	$150.65	$150.70
Purchase #7	$56.93	5.831%	$60.2496	$60.25	$60.25	$60.20
7 purchase totals =	$1,003.09		$1,098.9554	$1,098.95	$1,098.90	$1,099.00