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	$237.72	10.225%	$262.0269	$262.03	$262.05	$262.00
Purchase #2	$232.89	3.113%	$240.1399	$240.14	$240.15	$240.10
Purchase #3	$8.55	3.266%	$8.8292	$8.83	$8.85	$8.80
Purchase #4	$234.94	12.513%	$264.338	$264.34	$264.35	$264.30
Purchase #5	$170.74	11.793%	$190.8754	$190.88	$190.90	$190.90
Purchase #6	$41.89	5.179%	$44.0595	$44.06	$44.05	$44.10
Purchase #7	$63.70	10.641%	$70.4783	$70.48	$70.50	$70.50
7 purchase totals =	$990.43		$1,080.7472	$1,080.76	$1,080.85	$1,080.70