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	$65.66	9.749%	$72.0612	$72.06	$72.05	$72.10
Purchase #2	$165.31	8.249%	$178.9464	$178.95	$178.95	$178.90
Purchase #3	$73.72	12.111%	$82.6482	$82.65	$82.65	$82.60
Purchase #4	$92.43	11.467%	$103.0289	$103.03	$103.05	$103.00
Purchase #5	$244.90	3.579%	$253.665	$253.67	$253.65	$253.70
Purchase #6	$166.74	9.425%	$182.4552	$182.46	$182.45	$182.50
Purchase #7	$93.61	3.499%	$96.8854	$96.89	$96.90	$96.90
7 purchase totals =	$902.37		$969.6903	$969.71	$969.70	$969.70