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	$249.56	10.571%	$275.941	$275.94	$275.95	$275.90
Purchase #2	$139.44	8.607%	$151.4416	$151.44	$151.45	$151.40
Purchase #3	$218.72	10.548%	$241.7906	$241.79	$241.80	$241.80
Purchase #4	$75.88	8.669%	$82.458	$82.46	$82.45	$82.50
Purchase #5	$27.38	10.486%	$30.2511	$30.25	$30.25	$30.30
Purchase #6	$118.78	6.628%	$126.6527	$126.65	$126.65	$126.70
Purchase #7	$169.52	11.120%	$188.3706	$188.37	$188.35	$188.40
7 purchase totals =	$999.28		$1,096.9056	$1,096.90	$1,096.90	$1,097.00