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	$57.53	3.447%	$59.5131	$59.51	$59.50	$59.50
Purchase #2	$61.37	9.818%	$67.3953	$67.40	$67.40	$67.40
Purchase #3	$95.48	12.410%	$107.3291	$107.33	$107.35	$107.30
Purchase #4	$203.32	13.698%	$231.1708	$231.17	$231.15	$231.20
Purchase #5	$80.69	6.511%	$85.9437	$85.94	$85.95	$85.90
Purchase #6	$22.72	5.248%	$23.9123	$23.91	$23.90	$23.90
Purchase #7	$92.91	11.251%	$103.3633	$103.36	$103.35	$103.40
7 purchase totals =	$614.02		$678.6276	$678.62	$678.60	$678.60