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	$236.82	10.751%	$262.2805	$262.28	$262.30	$262.30
Purchase #2	$42.28	5.816%	$44.739	$44.74	$44.75	$44.70
Purchase #3	$196.27	12.105%	$220.0285	$220.03	$220.05	$220.00
Purchase #4	$29.32	9.284%	$32.0421	$32.04	$32.05	$32.00
Purchase #5	$169.40	6.781%	$180.887	$180.89	$180.90	$180.90
Purchase #6	$218.33	13.799%	$248.4574	$248.46	$248.45	$248.50
Purchase #7	$27.69	7.118%	$29.661	$29.66	$29.65	$29.70
7 purchase totals =	$920.11		$1,018.0955	$1,018.10	$1,018.15	$1,018.10