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	$105.72	8.563%	$114.7728	$114.77	$114.75	$114.80
Purchase #2	$170.90	13.687%	$194.2911	$194.29	$194.30	$194.30
Purchase #3	$40.41	7.463%	$43.4258	$43.43	$43.45	$43.40
Purchase #4	$101.83	3.219%	$105.1079	$105.11	$105.10	$105.10
Purchase #5	$11.75	11.818%	$13.1386	$13.14	$13.15	$13.10
Purchase #6	$27.89	9.671%	$30.5872	$30.59	$30.60	$30.60
Purchase #7	$24.46	5.779%	$25.8735	$25.87	$25.85	$25.90
7 purchase totals =	$482.96		$527.1969	$527.20	$527.20	$527.20