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	$70.65	3.177%	$72.8946	$72.89	$72.90	$72.90
Purchase #2	$216.95	9.403%	$237.3498	$237.35	$237.35	$237.30
Purchase #3	$67.73	7.117%	$72.5503	$72.55	$72.55	$72.60
Purchase #4	$154.77	10.692%	$171.318	$171.32	$171.30	$171.30
Purchase #5	$53.86	7.543%	$57.9227	$57.92	$57.90	$57.90
Purchase #6	$240.26	10.316%	$265.0452	$265.05	$265.05	$265.00
Purchase #7	$201.39	3.840%	$209.1234	$209.12	$209.10	$209.10
7 purchase totals =	$1,005.61		$1,086.2040	$1,086.20	$1,086.15	$1,086.10