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	$178.51	3.293%	$184.3883	$184.39	$184.40	$184.40
Purchase #2	$122.53	4.209%	$127.6873	$127.69	$127.70	$127.70
Purchase #3	$105.72	3.742%	$109.676	$109.68	$109.70	$109.70
Purchase #4	$218.59	3.338%	$225.8865	$225.89	$225.90	$225.90
Purchase #5	$98.49	10.281%	$108.6158	$108.62	$108.60	$108.60
Purchase #6	$34.49	8.172%	$37.3085	$37.31	$37.30	$37.30
Purchase #7	$244.97	8.346%	$265.4152	$265.42	$265.40	$265.40
7 purchase totals =	$1,003.30		$1,058.9776	$1,059.00	$1,059.00	$1,059.00