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	$130.80	10.687%	$144.7786	$144.78	$144.80	$144.80
Purchase #2	$90.69	9.221%	$99.0525	$99.05	$99.05	$99.10
Purchase #3	$182.43	11.761%	$203.8856	$203.89	$203.90	$203.90
Purchase #4	$169.31	8.546%	$183.7792	$183.78	$183.80	$183.80
Purchase #5	$92.56	10.549%	$102.3242	$102.32	$102.30	$102.30
Purchase #6	$218.31	10.422%	$241.0623	$241.06	$241.05	$241.10
Purchase #7	$209.38	5.318%	$220.5148	$220.51	$220.50	$220.50
7 purchase totals =	$1,093.48		$1,195.3972	$1,195.39	$1,195.40	$1,195.50