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	$47.51	12.789%	$53.5861	$53.59	$53.60	$53.60
Purchase #2	$166.57	3.393%	$172.2217	$172.22	$172.20	$172.20
Purchase #3	$150.96	3.701%	$156.547	$156.55	$156.55	$156.50
Purchase #4	$100.86	13.263%	$114.2371	$114.24	$114.25	$114.20
Purchase #5	$42.53	11.180%	$47.2849	$47.28	$47.30	$47.30
Purchase #6	$38.47	8.355%	$41.6842	$41.68	$41.70	$41.70
Purchase #7	$145.41	3.579%	$150.6142	$150.61	$150.60	$150.60
7 purchase totals =	$692.31		$736.1752	$736.17	$736.20	$736.10