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	$200.26	9.240%	$218.764	$218.76	$218.75	$218.80
Purchase #2	$248.52	6.533%	$264.7558	$264.76	$264.75	$264.80
Purchase #3	$123.85	7.714%	$133.4038	$133.40	$133.40	$133.40
Purchase #4	$39.29	12.150%	$44.0637	$44.06	$44.05	$44.10
Purchase #5	$119.65	9.161%	$130.6111	$130.61	$130.60	$130.60
Purchase #6	$79.53	13.297%	$90.1051	$90.11	$90.10	$90.10
Purchase #7	$233.50	12.345%	$262.3256	$262.33	$262.35	$262.30
7 purchase totals =	$1,044.60		$1,144.0291	$1,144.03	$1,144.00	$1,144.10