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	$72.50	4.704%	$75.9104	$75.91	$75.90	$75.90
Purchase #2	$170.82	4.469%	$178.4539	$178.45	$178.45	$178.50
Purchase #3	$171.98	11.535%	$191.8179	$191.82	$191.80	$191.80
Purchase #4	$31.56	10.534%	$34.8845	$34.88	$34.90	$34.90
Purchase #5	$111.36	12.468%	$125.2444	$125.24	$125.25	$125.20
Purchase #6	$162.88	13.619%	$185.0626	$185.06	$185.05	$185.10
Purchase #7	$241.33	7.406%	$259.2029	$259.20	$259.20	$259.20
7 purchase totals =	$962.43		$1,050.5766	$1,050.56	$1,050.55	$1,050.60