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	$45.81	3.416%	$47.3749	$47.37	$47.35	$47.40
Purchase #2	$198.83	4.724%	$208.2227	$208.22	$208.20	$208.20
Purchase #3	$177.88	10.490%	$196.5396	$196.54	$196.55	$196.50
Purchase #4	$25.59	6.319%	$27.207	$27.21	$27.20	$27.20
Purchase #5	$86.76	6.685%	$92.5599	$92.56	$92.55	$92.60
Purchase #6	$47.55	11.865%	$53.1918	$53.19	$53.20	$53.20
Purchase #7	$196.90	12.121%	$220.7662	$220.77	$220.75	$220.80
7 purchase totals =	$779.32		$845.8621	$845.86	$845.80	$845.90