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	$163.63	10.218%	$180.3497	$180.35	$180.35	$180.30
Purchase #2	$42.33	4.384%	$44.1857	$44.19	$44.20	$44.20
Purchase #3	$151.67	11.579%	$169.2319	$169.23	$169.25	$169.20
Purchase #4	$83.79	6.804%	$89.4911	$89.49	$89.50	$89.50
Purchase #5	$59.55	3.411%	$61.5813	$61.58	$61.60	$61.60
Purchase #6	$152.43	6.522%	$162.3715	$162.37	$162.35	$162.40
Purchase #7	$46.84	12.804%	$52.8374	$52.84	$52.85	$52.80
7 purchase totals =	$700.24		$760.0486	$760.05	$760.10	$760.00