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	$61.36	5.792%	$64.914	$64.91	$64.90	$64.90
Purchase #2	$81.60	13.249%	$92.4112	$92.41	$92.40	$92.40
Purchase #3	$156.70	6.146%	$166.3308	$166.33	$166.35	$166.30
Purchase #4	$229.93	4.620%	$240.5528	$240.55	$240.55	$240.60
Purchase #5	$182.38	9.137%	$199.0441	$199.04	$199.05	$199.00
Purchase #6	$126.85	13.854%	$144.4238	$144.42	$144.40	$144.40
Purchase #7	$73.74	6.310%	$78.393	$78.39	$78.40	$78.40
7 purchase totals =	$912.56		$986.0697	$986.05	$986.05	$986.00