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	$135.81	12.236%	$152.4277	$152.43	$152.45	$152.40
Purchase #2	$155.61	4.235%	$162.2001	$162.20	$162.20	$162.20
Purchase #3	$126.58	4.525%	$132.3077	$132.31	$132.30	$132.30
Purchase #4	$139.44	11.498%	$155.4728	$155.47	$155.45	$155.50
Purchase #5	$154.98	13.419%	$175.7768	$175.78	$175.80	$175.80
Purchase #6	$25.65	11.511%	$28.6026	$28.60	$28.60	$28.60
Purchase #7	$227.89	12.395%	$256.137	$256.14	$256.15	$256.10
7 purchase totals =	$965.96		$1,062.9247	$1,062.93	$1,062.95	$1,062.90