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	$39.31	5.500%	$41.4721	$41.47	$41.45	$41.50
Purchase #2	$234.28	4.869%	$245.6871	$245.69	$245.70	$245.70
Purchase #3	$61.64	9.498%	$67.4946	$67.49	$67.50	$67.50
Purchase #4	$100.96	4.152%	$105.1519	$105.15	$105.15	$105.20
Purchase #5	$47.48	10.278%	$52.36	$52.36	$52.35	$52.40
Purchase #6	$149.37	8.593%	$162.2054	$162.21	$162.20	$162.20
Purchase #7	$21.83	7.720%	$23.5153	$23.52	$23.50	$23.50
7 purchase totals =	$654.87		$697.8864	$697.89	$697.85	$698.00