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	$219.35	13.799%	$249.6181	$249.62	$249.60	$249.60
Purchase #2	$121.67	4.456%	$127.0916	$127.09	$127.10	$127.10
Purchase #3	$158.80	3.746%	$164.7486	$164.75	$164.75	$164.70
Purchase #4	$223.38	3.688%	$231.6183	$231.62	$231.60	$231.60
Purchase #5	$86.88	3.559%	$89.9721	$89.97	$89.95	$90.00
Purchase #6	$42.83	3.703%	$44.416	$44.42	$44.40	$44.40
Purchase #7	$172.69	6.681%	$184.2274	$184.23	$184.25	$184.20
7 purchase totals =	$1,025.60		$1,091.6921	$1,091.70	$1,091.65	$1,091.60