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	$227.88	7.727%	$245.4883	$245.49	$245.50	$245.50
Purchase #2	$244.66	10.677%	$270.7823	$270.78	$270.80	$270.80
Purchase #3	$29.27	8.606%	$31.789	$31.79	$31.80	$31.80
Purchase #4	$118.39	6.762%	$126.3955	$126.40	$126.40	$126.40
Purchase #5	$73.51	6.643%	$78.3933	$78.39	$78.40	$78.40
Purchase #6	$236.70	13.812%	$269.393	$269.39	$269.40	$269.40
Purchase #7	$57.76	9.497%	$63.2455	$63.25	$63.25	$63.20
7 purchase totals =	$988.17		$1,085.4869	$1,085.49	$1,085.55	$1,085.50