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	$71.65	6.150%	$76.0565	$76.06	$76.05	$76.10
Purchase #2	$61.47	9.306%	$67.1904	$67.19	$67.20	$67.20
Purchase #3	$174.42	13.746%	$198.3958	$198.40	$198.40	$198.40
Purchase #4	$184.90	6.803%	$197.4787	$197.48	$197.50	$197.50
Purchase #5	$75.47	4.554%	$78.9069	$78.91	$78.90	$78.90
Purchase #6	$85.84	8.270%	$92.939	$92.94	$92.95	$92.90
Purchase #7	$80.48	5.793%	$85.1422	$85.14	$85.15	$85.10
7 purchase totals =	$734.23		$796.1095	$796.12	$796.15	$796.10