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	$62.77	10.749%	$69.5171	$69.52	$69.50	$69.50
Purchase #2	$52.62	12.274%	$59.0786	$59.08	$59.10	$59.10
Purchase #3	$145.86	3.106%	$150.3904	$150.39	$150.40	$150.40
Purchase #4	$42.45	7.467%	$45.6197	$45.62	$45.60	$45.60
Purchase #5	$234.43	5.572%	$247.4924	$247.49	$247.50	$247.50
Purchase #6	$190.87	12.724%	$215.1563	$215.16	$215.15	$215.20
Purchase #7	$75.49	6.258%	$80.2142	$80.21	$80.20	$80.20
7 purchase totals =	$804.49		$867.4687	$867.47	$867.45	$867.50