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	$221.91	11.769%	$248.0266	$248.03	$248.05	$248.00
Purchase #2	$169.32	8.571%	$183.8324	$183.83	$183.85	$183.80
Purchase #3	$91.72	11.699%	$102.4503	$102.45	$102.45	$102.50
Purchase #4	$232.33	10.852%	$257.5425	$257.54	$257.55	$257.50
Purchase #5	$18.86	7.845%	$20.3396	$20.34	$20.35	$20.30
Purchase #6	$143.56	6.448%	$152.8167	$152.82	$152.80	$152.80
Purchase #7	$81.94	7.722%	$88.2674	$88.27	$88.25	$88.30
7 purchase totals =	$959.64		$1,053.2755	$1,053.28	$1,053.30	$1,053.20