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	$62.75	13.269%	$71.0763	$71.08	$71.10	$71.10
Purchase #2	$247.29	5.795%	$261.6205	$261.62	$261.60	$261.60
Purchase #3	$63.33	6.285%	$67.3103	$67.31	$67.30	$67.30
Purchase #4	$121.73	6.818%	$130.0296	$130.03	$130.05	$130.00
Purchase #5	$167.87	7.752%	$180.8833	$180.88	$180.90	$180.90
Purchase #6	$125.56	4.617%	$131.3571	$131.36	$131.35	$131.40
Purchase #7	$198.64	13.330%	$225.1187	$225.12	$225.10	$225.10
7 purchase totals =	$987.17		$1,067.3958	$1,067.40	$1,067.40	$1,067.40