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	$104.67	6.301%	$111.2653	$111.27	$111.25	$111.30
Purchase #2	$153.50	10.366%	$169.4118	$169.41	$169.40	$169.40
Purchase #3	$208.69	11.159%	$231.9777	$231.98	$232.00	$232.00
Purchase #4	$226.79	7.270%	$243.2776	$243.28	$243.30	$243.30
Purchase #5	$214.72	3.571%	$222.3877	$222.39	$222.40	$222.40
Purchase #6	$182.81	4.576%	$191.1754	$191.18	$191.20	$191.20
Purchase #7	$208.79	3.284%	$215.6467	$215.65	$215.65	$215.60
7 purchase totals =	$1,299.97		$1,385.1422	$1,385.16	$1,385.20	$1,385.20