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	$114.83	4.442%	$119.9307	$119.93	$119.95	$119.90
Purchase #2	$161.60	13.696%	$183.7327	$183.73	$183.75	$183.70
Purchase #3	$39.66	7.358%	$42.5782	$42.58	$42.60	$42.60
Purchase #4	$139.32	11.711%	$155.6358	$155.64	$155.65	$155.60
Purchase #5	$134.34	10.629%	$148.619	$148.62	$148.60	$148.60
Purchase #6	$113.29	13.304%	$128.3621	$128.36	$128.35	$128.40
Purchase #7	$228.48	13.436%	$259.1786	$259.18	$259.20	$259.20
7 purchase totals =	$931.52		$1,038.0371	$1,038.04	$1,038.10	$1,038.00