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	$110.35	4.677%	$115.5111	$115.51	$115.50	$115.50
Purchase #2	$178.47	6.765%	$190.5435	$190.54	$190.55	$190.50
Purchase #3	$248.78	5.543%	$262.5699	$262.57	$262.55	$262.60
Purchase #4	$59.60	5.175%	$62.6843	$62.68	$62.70	$62.70
Purchase #5	$96.41	6.716%	$102.8849	$102.88	$102.90	$102.90
Purchase #6	$45.49	11.767%	$50.8428	$50.84	$50.85	$50.80
Purchase #7	$170.42	11.790%	$190.5125	$190.51	$190.50	$190.50
7 purchase totals =	$909.52		$975.5490	$975.53	$975.55	$975.50