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	$240.41	5.621%	$253.9234	$253.92	$253.90	$253.90
Purchase #2	$92.89	7.546%	$99.8995	$99.90	$99.90	$99.90
Purchase #3	$70.44	8.747%	$76.6014	$76.60	$76.60	$76.60
Purchase #4	$201.52	6.852%	$215.3282	$215.33	$215.35	$215.30
Purchase #5	$156.99	13.725%	$178.5369	$178.54	$178.55	$178.50
Purchase #6	$7.93	3.405%	$8.2	$8.20	$8.20	$8.20
Purchase #7	$187.37	4.658%	$196.0977	$196.10	$196.10	$196.10
7 purchase totals =	$957.55		$1,028.5871	$1,028.59	$1,028.60	$1,028.50