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	$6.85	11.174%	$7.6154	$7.62	$7.60	$7.60
Purchase #2	$173.53	12.225%	$194.744	$194.74	$194.75	$194.70
Purchase #3	$223.52	9.819%	$245.4674	$245.47	$245.45	$245.50
Purchase #4	$165.55	12.189%	$185.7289	$185.73	$185.75	$185.70
Purchase #5	$244.32	3.461%	$252.7759	$252.78	$252.80	$252.80
Purchase #6	$46.94	13.383%	$53.222	$53.22	$53.20	$53.20
Purchase #7	$77.66	11.161%	$86.3276	$86.33	$86.35	$86.30
7 purchase totals =	$938.37		$1,025.8812	$1,025.89	$1,025.90	$1,025.80