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	$194.28	4.242%	$202.5214	$202.52	$202.50	$202.50
Purchase #2	$187.42	4.591%	$196.0245	$196.02	$196.00	$196.00
Purchase #3	$88.97	9.405%	$97.3376	$97.34	$97.35	$97.30
Purchase #4	$130.74	10.512%	$144.4834	$144.48	$144.50	$144.50
Purchase #5	$207.27	12.695%	$233.5829	$233.58	$233.60	$233.60
Purchase #6	$119.32	11.105%	$132.5705	$132.57	$132.55	$132.60
Purchase #7	$74.35	4.716%	$77.8563	$77.86	$77.85	$77.90
7 purchase totals =	$1,002.35		$1,084.3766	$1,084.37	$1,084.35	$1,084.40